Filler-Filled Highly Thermally Conductive Dispersion Composition Having Excellent Segregation Stability, Method for Producing Said Dispersion Composition, Filler-Filled Highly Thermally Conductive Material Using Said Dispersion Composition, Method for Producing Said Material, and Molded Article Obtained using Said Material

ABSTRACT

A filler-loaded thermal conductive liquid compositions formed by dispersing a powder composition, which contains polymer particles containing thermoplastic polymer particles, and thermal conductive filler particles containing particles having a graphite-like structure, obtained by pulverizing 5-70 parts by weight of the polymer particles and 30-95 parts by weight of the thermal conductive filler particles, the filler particles being covered with micronized polymer particles and the covered particles being uniformly dispersed, using 25-250 parts by weight of a liquid reactive dispersing medium and/or a dispersing medium containing a thermoplastic polymer having a deflection temperature under load or a melting point lower than the thermoplastic polymer used in the powder composition, and the liquid composition having conditions that a thermal conductive infinite cluster exhibiting a thermal conductivity of 1-35 w/mk is formed and a concentration of thermal conductive filler particles is equal to or more than a percolation threshold.

TECHNICAL FIELD

The present invention relates to a filler-loaded high thermal conductivedispersion liquid composition having excellent segregation stability andhaving fluidity at the time of cast molding or potting, a method forproducing the dispersion liquid composition, a filler-loaded highthermal conductive material using the dispersion liquid composition, amethod for producing the material, and a molded article obtained usingthe material. More specifically, the present invention relates to afiller-loaded high thermal conductive material dispersion liquidcomposition which has favorable segregation stability by control ofmorphology (polymer microstructure) and can form an advanced thermalconduction path.

BACKGROUND ART

Along with advancement in a remarkable decrease in size and a remarkableincrease in output of electric/electronic devices by the performanceenhancement, efficiency enhancement, and the like of semiconductorelements, a large amount of heat generated in accordance therewith hasbeen a problem. In particular, due to an increase in temperature by heatgenerated from coil portions in reactors for inverters and convertersand stators for drive motors for next-generation vehicles and anincrease in temperature by heat generated from semiconductor elementportions in power devices and high-luminance LED lights, varioustroubles such as an extreme decrease in efficiency, peeling-off at aninterface between different kinds of materials, and generation of crackshave been problems. Development of heat dissipating members andcomponents in the vicinity of semiconductor elements for coping withthose troubles has been an urgent problem, and particularly, variouscast molding resins and potting materials in which fluidity is impartedto materials have been developed.

For example, Patent Literature 1 discloses a reactor capable of ensuringheat dissipation properties of a coil and suppressing occurrence of anirreversible change such as cracking caused by low temperature andcompression due to vibration of the coil and a cast molding resin usedfor the reactor, formed from a urethane-based or epoxy-basedthermosetting resin, and having a glass transition temperature of −30°C. or lower and JIS A hardness at 25° C. of 20 or more and 52 or less.

Further, Patent Literature 2 discloses a cast molding resin composition,which contains, as essential components, a cationic polymerizationcatalyst and an ionic adsorbent for improving electrical characteristicsand strength of coil insulation, storage stability, and the like and isobtained by adding and mixing an inorganic filling material having athermal conductivity of 10 W/mK or more to an epoxy resin composition,and a rotating electrical machine in which the cast molding resincomposition is cured by cast molding the composition to a coil or a coilend. Furthermore, Patent Literature 3 discloses an epoxy resin moldingmaterial for sealing a motor, the material being excellent inproductivity and working environment and having favorable thermalresistance, thermal conductivity, high temperature water resistance, andreduction in a coefficient of linear expansion and being suitable forsealing a motor, and the material containing (A) an epoxy resin, (B) anepoxy resin curing agent, (C) a curing accelerator, (D) an inorganicfiller, (E) a silicone resin, (F) a thermoplastic resin, and (G) asilane coupling agent.

Furthermore, Patent Literature 4 discloses an insulating compositionwhich is relatively easily handled upon molding and has highadhesiveness to a metal such as copper and high thermal conductivity andin which a liquid crystalline polymer phase and a thermosetting polymerphase are separated and the liquid crystalline polymer phase forms acontinuous phase, and an insulating sheet containing the insulatingcomposition and a thermal conductive filler. In addition, PatentLiterature 5 discloses a thermal conductive thermosetting resincomposition having a composition viscosity in molding suppressed to alow value, hardly causing deterioration in excellent various physicalproperties such as thermal resistance and mechanical characteristicsinherent in a thermosetting epoxy resin, and having excellent thermalconductivity while covering the defects such as low toughness or lowcrack resistance inherent in the epoxy resin, the resin compositioncontaining a thermosetting epoxy resin (A), a thermosetting resin exceptthe thermosetting epoxy resin (A) or a thermoplastic resin (B), and ahigh thermal conductive inorganic filler (C), at least the thermosettingepoxy resin (A) forming a continuous phase.

Further, Patent Literature 6 discloses a coating liquid which contains acomposition obtained by pulverizing organic polymer particles containinga thermoplastic polymer and a thermal conductive filler having agraphite-like structure by using a pulverizing machine, which performsgrinding with frictional force or impact force, and a dispersing medium.

Furthermore, Patent Literature 7 discloses a method and an apparatus formolding which prevent the occurrence of a void in a molding resin bypreventing the air entrainment of the resin and the fouling or theclogging of a nozzle tip by free shots when a stator is molded by theresin.

CITATION LIST Patent Literatures

-   Patent Literature 1: JP 2015-204354 A-   Patent Literature 2: JP 2000-297204 A-   Patent Literature 3: JP 2009-155370 A-   Patent Literature 4: JP 2010-18679 A-   Patent Literature 5: JP 2010-132838 A-   Patent Literature 6: JP 2017-008321 A-   Patent Literature 7: JP 2008-260190 A

SUMMARY OF INVENTION Technical Problem

As described above, in order to cope with a decrease in size and anincrease in output of electric/electronic devices and to solve a problemof heat generation of a coil portion of a reactor or a stator, heatdissipation properties, segregation stability, workability, thermalresistance, mechanical characteristics, electrical characteristics, andthe like of a cast molding resin or a potting material which can beinjected in a coil portion have been improved.

Meanwhile, progress of research development and practical realization ofnovel materials such as GaN and SiC having high electrical fieldresistance, high energy gap, high mobility, and the like in a recentpower semiconductor (power electronics) has been significant, and ascompared to a conventional Si-based material, the novel materials enableoperation under the conditions of a high frequency, a high voltage, anda high temperature and greatly contributes to a decrease in size and anincrease in efficiency of electric/electronic equipment. Further,compact design is required in moving vehicles such as automobiles,aircrafts, and unmanned aircrafts on which a drive source is placed, aproblem of heat generation is particularly important, and in response tothe development of the novel materials mentioned above, innovative novelheat dissipation materials that can cope with stricter variousrequirements are required.

A polymer material (resin) has been conventionally preferably used sincethe material is excellent in designability, but the thermal conductivityof the resin itself is extremely low and the resin is usually used as acomposite material added with a thermal conductive filler. In order toform a thermal conduction path for transferring heat in a material, itis necessary to add a certain amount (threshold of thermal conductivity)or more of a thermal conductive filler. Therefore, a viscosity of thecomposite material significantly increases, and there are problems inthat not only workability or the like deteriorates but also it isdifficult to remove air bubbles having a great effect on injection ofthe composite material to a gap or on thermal conductivity.

That is, in Patent Literature 1, there is only description that anadditive such as a filler is mixed as necessary, and there is nospecific description of an improvement in thermal conductivity of theresin. Further, also in Patent Literatures 2 and 3, the thermalconductivities of the resins added with a filler at a concentration of33 wt % in the former and a filler at a concentration of 75 to 77 wt %in the latter are small values, that is, 1.7 W/mK and 1.9 W/mK at most,respectively, and there is no description of fluidity such as aviscosity that is an indicator of workability.

Furthermore, in Patent Literature 4, it is shown that the resincomposition in which the liquid crystal polymer is formed as acontinuous phase slightly increases a thermal conductivity of the resin,but regarding cases of the high thermal conductive filler, it isdescribed only that a coating solution added with methyl ethyl ketone isobtained, a thermal conductive sheet to be obtained after dryingexhibits a high thermal conductivity, and the cases are not related to acast molding resin or a potting material.

Also, in Patent Literature 5, an increase in thermal conductivity of thecomposition is achieved by preferentially dispersing the high thermalconductive inorganic filler in the thermosetting resin that becomes acontinuous phase. However, since the thermosetting resin ispreferentially dispersed in the continuous phase, when the concentrationof the high thermal conductive filler is low, dispersion stability isdeteriorated as well as thermal conductivity deteriorating, and when theconcentration increases, the viscosity increases and workability isdeteriorated, which is not preferable. Also, regarding the thermalconductivity, a value of 3.3 W/mK at most is only reported.

Furthermore, in Patent Literature 6, although the powder resincomposition having a high thermal conductivity is obtained, thecomposition is dispersed in a general dispersing medium (diluent) inorder to have fluidity, it is necessary to remove the dispersing mediumafter coating, and the composition is not reasonable for being used as acast molding resin or a potting material. Further, in Patent Literature7, a method and an apparatus by which the occurrence of a void and thefouling or the clogging of a nozzle tip are prevented are onlymentioned, and there is no description on a resin.

In this regard, an object of the present invention is to provide adispersion liquid composition being excellent in fluidity andsegregation stability and a high thermal conductive material obtained byusing the dispersion liquid composition and being excellent in thermalconductivity, dissipation properties, electrical characteristics,thermal resistance, mechanical characteristics, thermal cycleproperties, two-color molding properties, and the like.

Solution to Problem

The present inventors have conducted intensive studies in order to solvethe above-described problems, and as a result, have found that highthermal conductive filler particles containing organic polymer particlesand thermal conductive filler particles having a graphite-like structureare pulverized using a pulverizing machine, which performs grinding withfrictional force or impact force, to obtain a powder compositionuniformly dispersed, the powder composition is uniformly dispersed in aliquid reactive dispersing medium and/or a dispersing medium containinga thermoplastic polymer having a deformation temperature under load or amelting point lower than that of the thermoplastic polymer used in thepowder composition to obtain a dispersion liquid composition excellentin segregation stability, and the dispersion liquid composition ismolded by heating, cooled, and solidified to obtain a high thermalconductive material excellent in thermal conductivity, heat dissipationproperties, electrical characteristics, thermal resistance, mechanicalcharacteristics, thermal cycle properties, two-color molding properties,and the like in which a thermal conductive filler-rich phase and athermal conductive filler-non-rich phase coexist, thereby completing thepresent invention.

More specifically, compatibility with a resin is usually enhanced bytreating a surface of a filler with a coupling agent; however, thepresent invention has been made to enhance compatibility with a resinused in a dispersing medium and improve segregation stability of adispersion liquid by not only using a filler in a powder composition butalso concurrently using a thermoplastic polymer, and to thereby improvephysical properties and enable two-color molding using different kindsof materials.

That is, the present invention achieves the above-described objects bythe following means.

(1) A filler-loaded high thermal conductive dispersion liquidcomposition being formed by uniformly dispersing a powder composition,which contains organic polymer particles containing thermoplasticpolymer particles, and high thermal conductive filler particles whichcontain filler particles having a graphite-like structure and isobtained by pulverizing 5 to 70 parts by weight of the organic polymerparticles and 30 to 95 parts by weight of the high thermal conductivefiller particles with respect to 100 parts by weight of the total amountof these components by using a pulverizing machine, which performsgrinding with frictional force or impact force, to cause delamination orcohesive failure while maintaining an average planar particle size ofthe filler particles having a graphite-like structure, in the powdercomposition, the vicinity of the high thermal conductive fillerparticles being covered with the micronized organic polymer particlesand the covered particles being uniformly dispersed, using 25 to 250parts by weight of a liquid reactive dispersing medium and/or adispersing medium containing a thermoplastic polymer having a deflectiontemperature under load or a melting point lower than that of thethermoplastic polymer used in the powder composition with respect to 100parts by weight of the powder composition, and

the dispersion liquid composition having conditions that a thermalconductive infinite cluster exhibiting a thermal conductivity of 1 to 35W/mK is formed and a concentration of the high thermal conductive fillerparticles is equal to or more than a percolation threshold;

(2) the filler-loaded high thermal conductive dispersion liquidcomposition described in the above item (1), in which the pulverizingmachine is a ball mill, a roller mill, a bead mill, or a medium mill;

(3) the filler-loaded high thermal conductive dispersion liquidcomposition described in the above item (1) or (2), in which thethermoplastic polymer particles used in the powder composition containat least one selected from the group consisting of a thermoplastic resinand a thermoplastic elastomer, all of which have crystallinity and/oraromaticity;

(4) the filler-loaded high thermal conductive dispersion liquidcomposition described in any one of the above items (1) to (3), in whichthe thermoplastic polymer particles used in the powder compositioncontain at least one selected from the group consisting of polyphenylenesulfide, polyethylene terephthalate, polybutylene terephthalate,polycarbonate, polyamide, polyethylene, and polypropylene;

(5) the filler-loaded high thermal conductive dispersion liquidcomposition described in any one of the above items (1) to (4), in whichthe filler particles having a graphite-like structure are hexagonalboron nitride particles and a thermal conductivity thereof is 1 to 25W/mK;

(6) the filler-loaded high thermal conductive dispersion liquidcomposition described in the above item (5), in which the high thermalconductive filler particles further contain magnesium oxide particles;

(7) the filler-loaded high thermal conductive dispersion liquidcomposition described in any one of the above items (1) to (4), in whichthe high thermal conductive filler particles contain graphite particlesand a thermal conductivity thereof is 3 to 35 W/mK;

(8) the filler-loaded high thermal conductive dispersion liquidcomposition described in the above item (7), in which the graphiteparticles contain natural graphite particles and/or artificial graphiteparticles;

(9) the filler-loaded high thermal conductive dispersion liquidcomposition described in the above item (8), in which the naturalgraphite particles contain scale-like graphite particles;

(10) the filler-loaded high thermal conductive dispersion liquidcomposition described in any one of the above items (1) to (9), in whichthe dispersing medium contains the reactive dispersing medium and thereactive dispersing medium contains an uncured thermosetting resin;

(11) the filler-loaded high thermal conductive dispersion liquidcomposition described in the above item (10), in which the uncuredthermosetting resin contains a benzoxazine resin and/or a phenol-basedepoxy resin;

(12) the filler-loaded high thermal conductive dispersion liquidcomposition described in the above item (10) or (11), in which theuncured thermosetting resin contains an epoxy reactive diluent and/or anepoxy-modified silicone resin;

(13) the filler-loaded high thermal conductive dispersion liquidcomposition described in any one of the above items (10) to (12), inwhich the reactive dispersing medium contains a curing agent;

(14) the filler-loaded high thermal conductive dispersion liquidcomposition described in the above item (13), in which the curing agentcontains at least one selected from the group consisting of anamine-modified silicone resin, an alcohol-modified silicone resin, and acarboxylic acid-modified silicone resin;

(15) the filler-loaded high thermal conductive dispersion liquidcomposition described in any one of the above items (10) to (14), inwhich the reactive dispersing medium contains a catalyst;

(16) the filler-loaded high thermal conductive dispersion liquidcomposition described in the above item (15), in which the catalystcontains an imidazole compound;

(17) the filler-loaded high thermal conductive dispersion liquidcomposition described in any one of the above items (1) to (9), in whichthe dispersing medium contains the thermoplastic polymer and adeflection temperature under load or a melting point of thethermoplastic polymer is lower than that of the thermoplastic polymerparticles used in the powder composition by 10° C. or more;

(18) the filler-loaded high thermal conductive dispersion liquidcomposition described in any one of the above items (1) to (17), inwhich a viscosity at a temperature at the time of cast molding orpotting is 100 mPa·s or more and 300 Pa·s or less;

(19) the filler-loaded high thermal conductive dispersion liquidcomposition described in any one of the above items (1) to (18), inwhich the thermal conductive infinite cluster is based on a high thermalconductive filler-rich phase mainly attributable to the powdercomposition; and

(20) A method for producing a filler-loaded high thermal conductivedispersion liquid composition, the method including:

a step (1) of obtaining a powder composition, which contains organicpolymer particles containing thermoplastic polymer particles, and highthermal conductive filler particles which contain filler particleshaving a graphite-like structure, by pulverizing 5 to 70 parts by weightof the organic polymer particles and 30 to 95 parts by weight of thehigh thermal conductive filler particles with respect to 100 parts byweight of the total amount of these components by using a pulverizingmachine, which performs grinding with frictional force or impact force,to cause delamination or cohesive failure while maintaining an averageplanar particle size of the filler particles having a graphite-likestructure, in the powder composition, the vicinity of the high thermalconductive filler particles being covered with the micronized organicpolymer particles and the covered particles being uniformly dispersed;and

a step (2) of uniformly dispersing the powder composition using 25 to250 parts by weight of a liquid reactive dispersing medium and/or adispersing medium containing a thermoplastic polymer having a deflectiontemperature under load or a melting point lower than that of thethermoplastic polymer particles used in the powder composition withrespect to 100 parts by weight of the powder composition to prepare adispersion liquid composition having conditions that a thermalconductive infinite cluster exhibiting a thermal conductivity of 1 to 35W/mK is formed and a concentration of the high thermal conductive filleris equal to or more than a percolation threshold.

(21) A filler-loaded high thermal conductive material being formed byuniformly dispersing a powder composition, which contains organicpolymer particles containing thermoplastic polymer particles, and highthermal conductive filler particles which contain filler particleshaving a graphite-like structure and is obtained by pulverizing 5 to 70parts by weight of the organic polymer particles and 30 to 95 parts byweight of the high thermal conductive filler particles with respect to100 parts by weight of the total amount of these components by using apulverizing machine, which performs grinding with frictional force orimpact force, to cause delamination or cohesive failure whilemaintaining an average planar particle size of the filler particleshaving a graphite-like structure, in the powder composition, thevicinity of the high thermal conductive filler particles being coveredwith the micronized organic polymer particles and the covered particlesbeing uniformly dispersed, using 25 to 400 parts by weight of a liquidreactive dispersing medium and/or a dispersing medium containing athermoplastic polymer having a deflection temperature under load or amelting point lower than that of the thermoplastic polymer used in thepowder composition with respect to 100 parts by weight of the powdercomposition, and by causing a dispersion liquid composition havingconditions that a thermal conductive infinite cluster exhibiting athermal conductivity of 1 to 35 W/mK is formed and a concentration ofthe high thermal conductive filler is equal to or more than apercolation threshold to react under a condition that the reactivedispersing medium forms a crosslinked polymer, and/or to be fluidized ata temperature that is equal to or lower than a deflection temperatureunder load or a melting point of the thermoplastic polymer particlesused in the powder composition and is equal to or higher than adeflection temperature under load or a melting point of thethermoplastic polymer used in the dispersing medium, then to be moldedby heating at a pressure of 0 to 1000 kgf/cm² and at a temperature equalto or higher than a deflection temperature under load or a melting pointof the thermoplastic polymer particles used in the powder composition,and cooled and solidified.

(22) the filler-loaded high thermal conductive material described in theabove item (21), in which the filler-loaded high thermal conductivematerial is formed from a high thermal conductive filler-rich phase anda high thermal conductive filler-non-rich phase and the high thermalconductive filler-rich phase forms a thermal conductive infinitecluster;

(23) the filler-loaded high thermal conductive material described in theabove item (21) or (22), in which the condition that the reactivedispersing medium forms a crosslinked polymer is that the reactivedispersing medium has a degree of cure of 80% or more;

(24) a method for producing a filler-loaded high thermal conductivematerial, the method including: a step (1) of obtaining a powdercomposition, which contains organic polymer particles containingthermoplastic polymer particles, and high thermal conductive fillerparticles which contain filler particles having a graphite-likestructure, by pulverizing 5 to 70 parts by weight of the organic polymerparticles and 30 to 95 parts by weight of the high thermal conductivefiller particles with respect to 100 parts by weight of the total amountof these components by using a pulverizing machine, which performsgrinding with frictional force or impact force, to cause delamination orcohesive failure while maintaining an average planar particle size ofthe filler particles having a graphite-like structure, in the powdercomposition, the vicinity of the high thermal conductive fillerparticles being covered with the micronized organic polymer particlesand the covered particles being uniformly dispersed; a step (2) ofuniformly dispersing the powder composition using 25 to 250 parts byweight of a liquid reactive dispersing medium and/or a dispersing mediumcontaining a thermoplastic polymer having a deflection temperature underload or a melting point lower than that of the thermoplastic polymerparticles used in the powder composition with respect to 100 parts byweight of the powder composition to prepare a dispersion liquidcomposition having conditions that a thermal conductive infinite clusterexhibiting a thermal conductivity of 1 to 35 W/mK is formed and aconcentration of the high thermal conductive filler particles is equalto or more than a percolation threshold;

a crosslinking step (3) of allowing the dispersion liquid composition toreact under a condition that the liquid reactive dispersing medium formsa crosslinked polymer; and/or a fluidizing step (4) of fluidizing thethermoplastic polymer used in the dispersing medium at a temperaturethat is equal to or lower than a deflection temperature under load or amelting point of the thermoplastic polymer used in the powdercomposition and is equal to or higher than a deflection temperatureunder load or a melting point of the thermoplastic polymer used in thedispersing medium; a step (5) of molding by heating the material formedin the crosslinking step (3) and/or the fluidizing step (4) at apressure of 0 to 1000 kgf/cm² and at a temperature equal to or higherthan a deflection temperature under load or a melting point of thethermoplastic polymer particles used in the powder composition; and

a step (6) of cooling and solidifying the material formed in the step(5);

(25) the method for producing a filler-loaded high thermal conductivematerial described in the above item (24), in which the condition thatthe reactive dispersing medium forms a crosslinked polymer is that thereactive dispersing medium has a degree of cure of 80% or more; and

(26) a molded article including the filler-loaded high thermalconductive material described in any one of the above items (21) to (23)or a filler-loaded high thermal conductive material produced by theproduction method described in the above item (24) or (25), the moldedarticle being used as a high thermal conductive/heat dissipationcomponent;

(27) the molded article described in the above item (26), in which themolded article is formed by laminating two layers of the filler-loadedhigh thermal conductive material,

one layer of the two layers has a thermal conductivity of 3 to 35 W/mKand exhibits electrical conductivity with a surface electricalconductivity of 70 (Ωcm)⁻¹ or less, and the other layer of the twolayers has a thermal conductivity of 1 to 25 W/mK and is a semiconductorhaving a surface electrical conductivity of 0.1 to 10⁻¹⁰ (Ωcm)⁻¹ orexhibits insulating properties with a surface electrical conductivity of10⁻¹⁰ (Ωcm)⁻¹ or less; and

(28) the molded article described in the above item (26) or (27), inwhich layers of the two layers of the filler-loaded high thermalconductive material are layers formed from gradient materials havingdifferent filler concentrations from each other.

Herein, the dispersion liquid composition is mainly configured from thepowder composition and the dispersing medium for uniformly dispersingthe powder composition. The organic polymer particles containingthermoplastic polymer particles, the high thermal conductive fillerparticles which contain filler particles having a graphite-likestructure, and the like are constituents of the powder composition andhave a particle shape in the state of the dispersion liquid. Since theliquid reactive dispersing medium containing an uncured thermosettingresin and/or the thermoplastic polymer having a lower melting point thanthe thermoplastic polymer used in the powder composition constitute thedispersing medium, these are important constituents for providingfluidity at the time of cast molding, potting, and the like, form acontinuous phase in the dispersion liquid at the time of cast molding orpotting, and control fluidity represented by a dispersion liquidviscosity.

Advantageous Effects of Invention

The filler-loaded high thermal conductive dispersion liquid compositionaccording to the present invention (hereinafter, also simply abbreviatedas “dispersion liquid composition”) is obtained by uniformly dispersingand stabilizing the powder composition formed from the organic polymerparticles and the high thermal conductive filler particles by using aliquid reactive dispersing medium having a low viscosity and/or athermoplastic polymer having a deflection temperature under load or amelting point lower than that of the thermoplastic polymer particlesused in the powder composition, and at the time of cast molding orpotting, the dispersing medium becomes a continuous phase and mainlycontrols fluidity.

In the powder composition, by covering the vicinity of the high thermalconductive filler particles having a high specific gravity with theorganic polymer particles containing micronized thermoplastic polymerparticles having a specific gravity close to the dispersing medium andhaving high affinity with the reactive dispersing medium and thethermoplastic polymer used as the dispersing medium, the sedimentationof the high thermal conductive filler particles and strong aggregationbetween the filler particles are suppressed, and segregation stabilityand storage stability are improved. As a result, it is easy to performinjection to a mold, potting to a device, and the like, and it ispossible to perform uniform insertion thoroughly in minute gaps, andthus not only workability but also stable product quality and highperformance inherent in a material can be exhibited. In particular, atthe time of injection to a mold or the like in accordance with a strongshear force and/or at a high temperature, separation or aggregation ofthe filler is suppressed, and uniform injection of a composite materialcan be performed.

Further, regarding the aforementioned dispersion liquid composition, atthe stage in which the reactive dispersing medium used as the dispersingmedium is crosslinked and/or the stage in which the thermoplasticpolymer used as the dispersing medium is fluidized, the initialconcentration of the high thermal conductive filler, which is aconstituent element of the powder composition, in the powder compositionis maintained, then at the stage in which the thermoplastic polymerparticles, which are other constituent elements of the powdercomposition, are heated to a temperature that is equal to or higher thanthe deflection temperature under load or the melting point, themicronized organic polymer part is softened and/or melted, then at thestage of cooling/solidifying, a sea-island structure formed from afiller-rich phase and a filler-non-rich phase is formed, the componenthaving high affinity with the filler thinly covers the vicinity of thehigh thermal conductive filler particles to become a filler-rich phase,and an advanced thermal conduction path in which the high thermalconductive filler is efficiently connected is formed.

That is, since the dispersion liquid composition is divided into thehigh thermal conductive filler-rich phase and the high thermalconductive filler-non-rich phase, a thermal conductive infinite clusterbased on the filler-rich phase is easily formed, and a percolationthreshold of thermal conductivity with respect to the concentration ofthe high thermal conductive filler particles is also lowered. Therefore,as compared to the case of containing no thermoplastic polymer particlesin the powder composition, the present invention exhibits a high thermalconductivity in the same concentration of the high thermal conductivefiller, can exert excellent properties also in mechanicalcharacteristics, thermal cycle properties, and the like by thefiller-rich phase and the filler-non-rich phase being relativelyuniformly dispersed, and achieves an increase in thermal conductivity byadvanced morphologic control.

Furthermore, in the case of performing two-color molding of compositematerials by using insulating filler particles and conductive fillerparticles as high thermal conductive filler particles or the case ofmolding composite materials (gradient materials) each having a differentfiller concentration, connection between the high thermal conductivefiller particles is promoted by presence of the filler-rich phase in theinterface therebetween, a thermal resistance at the interfacetherebetween is significantly reduced, and a mechanical strength can beimproved by reconstruction of morphology by softening and/or melting andcooling/solidifying of the resin component at the interface.

Furthermore, since the dispersion liquid composition of the presentinvention is excellent in segregation stability, not only workability isimproved, but also particles having a larger specific gravity can becontained as the high thermal conductive filler so that the thermalconductivity and the electrical conductivity can be improved. Inaddition, since a thermosetting resin and a thermoplastic resin whichhave various performances can be used as the dispersing medium, it ispossible to cope with various requirements particularly forelectric/electronic devices that are diversified.

Since the present invention is configured as described above, it ispossible to provide a product which has favorable workability,segregation stability, storage stability, and the like, penetrates intoa gap in a coil portion, an interface in casing, and the like withoutany gaps, enhances thermal conductivity or heat dissipation propertiesof a molded product thus obtained, and is excellent in electricalcharacteristics, toughness/elastic modulus, thermal resistance, thermalcycle properties, and the like, in the case of using the product for acast molding resin, a potting material (sealing material), an adhesive,grease, and the like. In particular, a material using an insulatingfiller is used for parts necessary for insulating properties of electricdevices having a coil portion of a reactor or a stator of a drive motor,an electric motor, a power generating motor, and the like, electronicdevices having a semiconductor substrate such as a power devices andhigh-luminance LED lights, and the like, a material using a conductivefiller is used for a radiating fin, a housing, and the like notnecessary for insulating properties, or both materials are integrallymolded so that an increase in temperature of a coil portion or asemiconductor element is efficiently prevented and this can contributeto an improvement in efficiency or a decrease in size of a device.Further, it is also possible to achieve prevention of failure,breakdown, or the like of electric/electronic devices and packaging ofdevices and electronic/electric devices excellent in waterproofproperty, dust proof property, and the like are obtainable. However,even when a conductive filler is used, in a case where the electricalconductivity of the material is low and the material has insulatingproperties or a case where the insulating properties of the coil portionare sufficiently guaranteed, the material can be used for partsnecessary for insulating properties. In addition, by using a resin, thematerial can be utilized as EMC-prevention component/member for noiseprevention, and can be useful for malfunction or the like of sensorsthat is concerned with widespread of automated driving and IoT.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates photographs showing results of SEM observation and Natom mapping of molded articles produced in Example 2 (fillerconcentration 40 wt %) and Example 4 (filler concentration 60 wt %).

FIG. 2 illustrates a photograph showing a result of SEM observation of amolded article produced in Example 26.

FIG. 3 illustrates photographs showing results of S, C, N, and O atommapping of a molded article produced in Example 26.

FIG. 4 illustrates photographs of stators without resin molding (left)and with resin molding (right) used in motor evaluation in Examples.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments for carrying out the present invention will bedescribed in detail.

<Filler-Loaded High Thermal Conductive Dispersion Liquid Composition>

According to an aspect of the present invention, there is provided afiller-loaded high thermal conductive dispersion liquid compositionhaving excellent segregation stability, the filler-loaded high thermalconductive dispersion liquid composition being formed by pulverizingorganic polymer particles containing thermoplastic polymer particles andhigh thermal conductive filler particles which contain filler particleshaving a graphite-like structure at a specific ratio by using a specificpulverizing machine to cause delamination or cohesive failure of thefiller particles while maintaining an average planar particle of thefiller particles having a graphite-like structure to obtain a powdercomposition in which the filler and the organic polymer are uniformlydispersed, and uniformly dispersing the powder composition by using aspecific amount of a reactive dispersing medium and/or a dispersingmedium containing a thermoplastic polymer with respect to the powdercomposition.

(Powder Composition)

The powder composition used in the present invention is mainlyconfigured by organic polymer particles and high thermal conductivefiller particles which contain filler particles having a graphite-likestructure, and exists as a solid moiety of a powder form when thedispersion liquid composition of the present invention is fluidized tobe injected or potted into a mold or the like. Then, a material (moldedarticle) formed from the dispersion liquid composition is obtained bycausing the dispersion liquid composition according to the presentinvention to be fluidized under a specific temperature condition, moldedat a specific temperature and at normal pressure or underpressurization, and cooled and solidified. In the material, afiller-rich phase and a filler-non-rich phase involving the high thermalconductive filler and/or the organic polymer that constitute the powdercomposition coexist and are uniformly distributed, and thus an advancedthermal conduction path can be formed and high thermal conductivity,excellent electrical characteristics, mechanical characteristics, andthe like can be exhibited.

[Organic Polymer Particles]

The average particle size of the organic polymer particles used in thepresent invention is usually 1 to 5000 μm and preferably 5 to 500 μm.When the average particle size of the organic polymer particles is 1 μmor more, no special apparatus for micronization is needed. On the otherhand, when the average particle size of the organic polymer particles is5000 μm or less, defective dispersion is not likely to occur at the timeof pulverizing and mixing. Organic polymer particles including lumpyobjects having a large particle size can be used after being pretreatedin advance by pulverization and/or crushing, classification, and thelike to obtain a desired average particle size. The organic polymerparticles preferably have an aromatic hydrocarbon structure similar tothe high thermal conductive filler particles having a graphite-likestructure, and it is particularly preferable to crystallize the organicpolymer in the vicinity of the filler in the presence of the filler,along the planar direction of the filler.

Examples of the organic polymer particles that can be used includethermoplastic polymers formed from a thermoplastic resin and anuncrosslinked elastomer, all of which are mainly formed fromthermoplastic polymer particles, have crystallinity and/or aromaticity,and are used in the field of molding. The melting point of thethermoplastic polymer used as the organic polymer particles is notparticularly limited, except that it is not lower than the melting pointof the thermoplastic resin used in the dispersing medium, but themelting point thereof is preferably 120° C. or higher, more preferably130 to 400° C., and particularly preferably 150 to 350° C. Thethermoplastic polymer becomes a solid content moiety in a state of beingin a dispersion liquid at the time of fluidization. Furthermore, theorganic polymer according to the present invention can contain athermosetting polymer formed from an uncured thermosetting resin and ispreferably in a solid state at the time of producing the powdercomposition. The melting point can be obtained from an endothermic peakat the time of melting using a differential scanning calorimeter (DSC)and a differential thermal analysis (DTA) apparatus, and a deflectiontemperature under load can be used as an indication of a non-crystallinepolymer showing no melting point.

Examples of the crystalline aromatic thermoplastic resin includearomatic polyesters such as polyethylene terephthalate, polybutyleneterephthalate, polytrimethylene terephthalate, polyethylene naphthalate,and liquid crystal polyester; and known thermoplastic polymers havingcrystallinity and aromaticity such as polyphenylene sulfide, aromaticpolyimide precursors, phenol (novolac type and the like) phenoxy resins,polyether ketone, polyether ether ketone, polystyrene,polybenzimidazole, and polyphenylene oxide. These resins areparticularly preferable since the resins can strongly fix the fillerparticle between fillers due to the crystallinity of the polymer grownonto the filler surface and/or compatibility with the filler in a casewhere affinity with the filler is high; electrical conductivity orinsulating properties, and thermal conductivity can be markedlyincreased without significantly impairing mechanical characteristics;and the coefficient of thermal expansion can be appropriatelycontrolled.

Examples of the crystalline thermoplastic resin include knownthermoplastic resins having crystallinity, such as polyolefins such aspolyethylene and polypropylene; polyoxymethylene, polyamide, polymethylmethacrylate, polyvinyl chloride, polyvinylidene chloride, polyketone;fluororesins such as polytetrafluoroethylene; cycloolefin polymers,polyacetal, and ultrahigh molecular weight polyethylene. These resinsare preferable since the resins can fix the filler particle betweenfillers due to the crystalline of the polymer grown onto the fillersurface in a case where affinity with the filler is high; electricalconductivity or insulating properties, and thermal conductivity can beincreased without impairing mechanical characteristics; and thecoefficient of thermal expansion can be appropriately controlled.

Examples of the non-crystalline aromatic thermoplastic resin includeknown thermoplastic polymers having aromatic substituents such aspolycarbonate, polyphenylene ether, polyarylate, polysulfone, polyethersulfone, polyether imide, polyamideimide, and liquid crystal polymers.Since these resins have a structure similar to that of the high thermalconductive filler, in a case where affinity with the filler is high, theresins are crystallized, in the presence of a high thermal conductivefiller, on the surface and/or in the vicinity of the high thermalconductive filler, or even if crystallization is not attained as a wholesystem, the resins have high compatibility with the high thermalconductive filler having a similar structure, and thus the resins arefavorably in close contact with the filler. Therefore, the resins arepreferable since they can increase the electrical conductivity orinsulating properties and thermal conductivity and can control thecoefficient of thermal expansion without significantly impairingmechanical characteristics, by fixing the filler between fillers on thesurface and/or in the vicinity of the filler. Although crystallizationfrequently occurs at micro units and the melting point can be confirmedby aging, in a case where the melting point cannot be confirmed, thedeflection temperature under load can be measured and used as anindication.

Examples of the uncrosslinked elastomer include known elastomersincluding thermoplastic elastomers having aromatic substituents and/orcrystalline olefin moieties, such as polystyrene-based,polyolefin-based, polyurethane-based, polyester-based, polyamide-based,polybutadiene-based, polyisoprene-based, silicone-based, andfluorine-based elastomers; and graft copolymers containing olefin-basedpolymer segments formed from α-olefin monomers and vinyl-based polymersegments formed from vinyl-based monomers.

Examples of the uncured thermosetting resin include known thermosettingresin precursors such as an unsaturated polyester resin, a vinyl esterresin, an epoxy resin, a phenol (resol type) resin, a urea/melamineresin, a polyimide resin, a benzoxazine resin, and mixture thereof, allof which have aromatic substituents. Since the thermosetting resinprecursors are usually oligomers having small molecular weights, in thecase of using the precursors in combination with thermoplastic polymersand/or thermoplastic elastomers having large molecular weights, fluidityin the system is increased before curing, thereby increasingpenetrability of the polymer in between the filler layers. Further,adhesiveness between fillers or between different kinds of materials isenhanced by the functional groups formed along with the curing reaction.

The thermoplastic resin, the uncrosslinked elastomer, and the uncuredthermosetting resin described above, all of which have crystallinityand/or aromaticity, may be copolymers or modification products, and mayalso be a resin obtained by blending two or more kinds thereof. Further,for an enhancement of impact resistance, a resin obtained by adding anelastomer or a rubber component to the thermosetting resin may also beused.

Among uncured thermosetting resins, particularly, a benzoxazine resinhas excellent thermal resistance, and since curing proceeds as a resultof an addition reaction, volatile side products are not generated.Further, the reaction also proceeds in the absence of catalyst, and auniform and compact resin phase can be formed, which is preferable.Furthermore, when the benzoxazine resin is used in combination with anepoxy resin, the benzoxazine resin acts as a curing accelerator for theepoxy resin, and defects of the epoxy resin in terms of thermalresistance, strength, and the like can be compensated.

The benzoxazine is a compound having a dihydro-1,3-benzoxazine ring(hereinafter, also simply referred to as “oxazine ring”), and is acondensate of amines, phenols, and formaldehydes. Usually, the chemicalstructure of benzoxazine to be produced is determined by substituents,kinds, and the like of phenols, amines, and the like, which are reactionraw materials thereof. The benzoxazine used in the present invention maybe any derivative of an “oxazine ring” and is not particularly limited,but a compound having at least two oxazine rings in one molecule ispreferred. The reason for this is that the crosslinking density isincreased and superior results such as an improvement in thermalresistance are obtained. Specific examples of the benzoxazine include Pdtype benzoxazine and Fa type benzoxazine manufactured by SHIKOKUCHEMICALS CORPORATION, and the like.

As the amines for deriving benzoxazine having at least two oxazinerings, diamines can be used. Examples of the diamines include4,4′-oxydianiline, 4,4′-diaminodiphenylmethane, para-diaminobenzene,compounds obtained by substituting the foregoing compounds with an alkylgroup, an alkoxy group, a halogen, an aromatic hydrocarbon group, or thelike, and the like. Among these, it is preferable to use4,4′-diaminodiphenylmethane.

Examples of phenols include, as monovalent phenols, phenol, cresol,xylenol, naphthol, and the like; and as polyvalent phenols, bisphenols;and compounds obtained by substituting the foregoing compounds with analkyl group, an alkoxy group, a halogen, an aromatic hydrocarbon group,and the like. Specific examples of the bisphenols include bisphenol A,bisphenol F, bisphenol S, and the like. Among these, it is preferable touse phenol and bisphenol.

Regarding formaldehydes, formaldehyde (aqueous solution),para-formaldehyde, and the like are used. Among these, it is preferableto use formaldehyde.

In order to obtain benzoxazine from the amines, phenols, formaldehydesas described above, a wide variety of known methods can be employed.

A benzoxazine having at least two oxazine rings can be produced by amethod of allowing a diamine, a phenol, and a formaldehyde to react, amethod of allowing a bisphenol, a primary amine, and a formaldehyde toreact, or the like.

The organic polymer particles formed from a thermoplastic resin, athermoplastic elastomer, and/or a thermosetting resin areuncrosslinked/uncured particles in the mixture. Further, as will bedescribed, when the mixture is molded by heating under pressure, thethermoplastic resin may be crosslinked, and the thermoplastic elastomeror thermosetting resin is usually crosslinked/cured and then used.

Among these organic polymer particles, for organic polymer particlesthat have high thermal resistance, strongly fix the filler particlebetween fillers, and enhance various physical properties such as heatconductivity and electrical characteristics, polyethylene terephthalate,polybutylene terephthalate, polyphenylene sulfide, polycarbonate,polyamide, polypropylene, polyethylene, and benzoxazine are suitable.When the various polymer particles described above are used incombination in accordance with the purpose of use, the features oforganic polymers can be exhibited at the maximum.

[High Thermal Conductive Filler Particles]

The high thermal conductive filler particles used in the presentinvention contain filler particles having a graphite-like structure, andare preferably filler particles alone exhibiting a thermal conductivityof 10 W/mK or more. The average particle size thereof is 1 to 2000 μmand preferably 3 to 200 μm. When the average particle size of the highthermal conductive filler particles is 1 μm or more, the surface area isdecreases, and the loss of heat and electrical conduction at the fillerinterface can be reduced. On the other hand, when the average particlesize of the thermal conductive filler is 2000 μm or less, it ispreferable because defective dispersion is not likely to occur. In thepresent invention, high thermal conductive filler particles other thanthe filler particles having a graphite-like structure can beconcurrently used, and examples thereof include ceramic filler particlesand metal filler particles which are typically used and have highthermal conductive properties.

The filler particles having a graphite-like structure used in thepresent invention are an anisotropic material, usually have slidingproperties, and serve for prevention of breakage or cracks at aninterface between a coil, a substrate, or the like and a metal whenmechanical impact is applied by vibration, thermal cycles, and the like.As the filler particles having a graphite-like structure, known thermalconductive fillers having a graphite-like structure which are used inthe field of molding and are formed from black leads (synonym forgraphite) that usually have electrical conductivity, such as naturalgraphite such as scale-like graphite, bulk graphite, and soil graphite,and artificial graphite; thermal conductive ceramics that usually haveinsulating properties, such as hexagonal boron nitride, hexagonalsilicon carbide, and hexagonal silicon nitride; sulfides such asmolybdenum disulfide and tungsten disulfide; and mixtures thereof, canbe used without any particular limitations. In general, a materialhaving an electrical conductivity of 10⁶ to 10² (Ωcm)⁻¹ is called aconductor, a material having an electrical conductivity of 10 to 10⁻⁷(Ωcm)⁻¹ is called a semiconductor, and a material having an electricalconductivity of 10⁻¹⁰ to 10⁻¹⁸ (Ωcm)⁻¹ is called an insulator, and amongthe aforementioned fillers, scale-like graphite, artificial graphite,and hexagonal boron nitride are particularly preferred since theyproduce high thermal conductive materials having high electricalconductivity or high insulating properties, respectively.

The scale-like graphite is scale-shaped graphite produced mainly frommines in China, the United States, India, Brazil, and the like andhaving a large aspect ratio, and in general, larger scales areassociated with higher thermal resistance. Graphite having an averageparticle size of about 8 to 200 μm and a carbon content of 85 to 99% isfrequently sold in the market, and this graphite is anisotropic but hasa high thermal conductivity of 200 W/mK or more.

Artificial graphite is black leads obtained by molding a mixture ofpowdered cokes and pitch, and artificially developing crystals through ahigh temperature calcination process at about 3000° C., and has fewerimpurities and high hardness.

Hexagonal boron nitride is a white powder having a scale-like crystalstructure resembling graphite, and is a chemically stable materialcalled “white graphite.” Hexagonal boron nitride is a material havingexcellent thermal conductivity, thermal resistance, corrosionresistance, electrical insulating properties and lubricating/moldreleasing properties, and is widely used as an additive material invarious matrices. Thus, known materials can be used without any change.A scale-like form or a polygonal plate form is generally used, and thereare also available aggregate powders in which primary particles arecompositely aggregated. Although the substance is anisotropic, a moldedbody thereof has a high bulk thermal conductivity of about 60 W/mK.

As high thermal conductive filler particles other than the fillerparticles having a graphite-like structure, there are mentioned ceramicfiller particles, which are usually used as an isotropic insulatingmaterial, such as aluminum nitride, aluminum oxide (also referred to asalumina), magnesium oxide (also referred to as magnesia), berylliumoxide (also referred to as beryllia), crystalline silica, and cubicboron nitride, and mixtures thereof; and metal filler particles, whichare usually used as a conductive material, such as silver, copper,aluminum, zinc, nickel, iron, tin, and a copper alloy, and mixturesthereof, all of which are used as a high thermal conductive filler.Usually, combinations of these high thermal conductive filler particlescan sufficiently exhibit respective properties when insulating fillersor conductive fillers are used, which is preferable. Among these, as aninsulating material, for use in combination with hexagonal boronnitride, magnesium oxide that is soft and does not damage a coil portionis particularly preferred.

For high thermal conductive filler particles including lumpy objectshaving large particle sizes, it is preferable to use the filler afterpretreating the filler in advance by pulverization and/or crushing,classification, and the like, and adjusting the particles to a desiredaverage particle size. Known methods for promoting an increase inthermal conductivity by concurrently using high thermal conductivefiller particles having different particle sizes or controlling thefiller shape can also be used.

(Method for Preparing Powder Composition)

The powder composition according to the present aspect can be preparedby pulverizing organic polymer particles containing thermoplasticpolymer particles and high thermal conductive filler particles whichcontain filler particles having a graphite-like structure as necessary,and then mixing these components. However, when mixing is conducted byusing excessively large force, micronization occurs, and thus surfaceareas of the high thermal conductive filler particles significantlyincrease and inhibition of thermal conduction occurs at the particleinterfaces, which is not preferable. Thus, in the present aspect, it ispreferable to mix the components by a method of uniformly dispersing thehigh thermal conductive filler in the composition while maintaining theaverage planar particle size of the filler particles having agraphite-like structure. As the mixing method, a method of usingdelamination and/or cohesive failure of a filler is preferably used.Incidentally, the ratio of the thermoplastic polymer particles in theorganic polymer particles is preferably 20 wt % or more, more preferably50 wt % or more, and further preferably 80 wt % or more. In addition,the ratio of the filler having a graphite-like structure in the highthermal conductive filler is preferably 20 wt % or more, more preferably50 wt % or more, and further preferably 80 wt % or more. The reason forthis is that, when the ratios thereof are 20 wt % or more, properties ofthe thermoplastic polymer and the filler having a graphite-likestructure can be exhibited.

Examples of the method of mixing the organic polymer particles, the highthermal conductive filler particles, and the like include a method ofintroducing the materials into a bag or a can and manually mixing thematerials; a method of using a tumbler or the like; a method of using apowder mixing machine such as a Henschel mixer, a Super mixer, or ahigh-speed mixer; a method of using a pulverizing machine such as a jetmill, an impact mill, an attrition mill, an air classification (ACM)mill, a ball mill, a roller mill, a bead mill, a medium mill, acentrifuge mill, a cone mill, a disc mill, a hammer mill, or a pin mill;methods combining these; and the like. The method of using a pulverizingmachine is capable of uniform mixing since large forces such ascompressive force, shear force, impact force, and frictional force areapplied to powder particles, and is preferable for the present inventionsince the method is capable of micronizing the organic polymer particlesor causing a cohesive failure of the filler; however, in the case ofusing a pulverizing machine having large fracturing force, it isnecessary to specially control the pulverizing machine in order tomaintain an average planar particle size of the filler particles. Inparticular, the method of using a ball mill, a roller mill, a bead mill,or a medium mill is particularly preferred in the point of view that themethod is capable of maintaining the average planar particle size of thefiller particles without special control and micronizing relatively softorganic polymer particles to cause the micronized particles to adhere tothe vicinity of the filler particles.

In general, a ball mill is an apparatus for producing a powder dispersedby grinding down a material adhering to ball surfaces using frictionalforce or impact force, by introducing hard balls made of a ceramic orthe like and powders of materials into a cylindrical vessel, androtating the vessel. It is possible to uniformly disperse components bydelamination or cohesive failure while simply and efficientlymaintaining the average planar particle size of the filler particleshaving a graphite-like structure, which is preferable. It is notparticularly necessary to strictly control the size or shape of the rawmaterials used at the time of mixing and pulverization. However, it ispreferable to use a size or shape in a preliminarily determined range inorder to maintain the product quality.

The mixing time is not particularly limited, but is preferably 0.2 to 15hours and more preferably 0.5 to 5 hours.

Further, the average particle size of a uniform powder composition(organic polymer particles and high thermal conductive filler particles)obtained by pulverization is preferably 0.5 to 1000 μm, and morepreferably 1 to 500 μm. When the average particle size of thecomposition is 0.5 μm or more, the contact area between fillers isdecreased by a decrease in the surface area so that deterioration ofthermal conductivity and electrical characteristics caused by the lossinduced by contact can be prevented. On the other hand, when the averageparticle size of the composition is 1000 μm or less, the resin isuniformly dispersed so that a decrease in strength caused by defectivecontact between the resin and the filler can be prevented. At this time,the high thermal conductive filler according to the present invention isstrong against a force applied from a direction perpendicular to theplane and maintains an average planar particle size; however, thecohesive force in all directions of the organic polymer particles isweaker than that of the filler so that the organic polymer particles aremicronized to have an average particle size equal to or less than theaverage particle size of the high thermal conductive filler particles,and the organic polymer particles are in a state of covering thevicinity of the filler.

Regarding the ratios of the organic polymer particles and the highthermal conductive filler particles in the powder composition used inthe present invention, with respect to 100 parts by weight of the totalamount, the ratio of the organic polymer particles is 5 to 70 parts byweight and preferably 10 to 50 parts by weight, and the ratio of thehigh thermal conductive filler particles is 30 to 95 parts by weight andpreferably 50 to 90 parts by weight. When the ratio of the organicpolymer particles is less than 5 parts by weight and the ratio of thehigh thermal conductive filler particles is more than 95 parts byweight, it is difficult to cover the vicinity of the high thermalconductive filler particles with the organic polymer particles. When theratio of the organic polymer particles is more than 70 parts by weightand the ratio of the high thermal conductive filler particles is lessthan 30 parts by weight, the organic polymer particles exist in a largeamount in an interface of the high thermal conductive filler particles,and as a result, the connection between the filler particles isinhibited so that a thermal conduction path is difficult to form.

In the powder composition used in the present invention, knownadditives, reinforcing agents, and/or fillers can be appropriately usedas necessary, to the extent that the addition does not causecontradiction to the purpose of the present invention. Examples of theadditives may include a mold releasing agent, a flame retardant, anantioxidant, an emulsifier, a softening agent, a plasticizing agent, asurfactant, a coupling agent, a compatibilizer, and the like. Examplesof the reinforcing materials may include short fibers formed from glassfibers, carbon fibers, metal fibers, and inorganic fibers. Examples ofother fillers may include calcium carbonate (limestone), glass, talc,silica, mica, diamond, carbon nanotube, carbon nanofibers, graphene,ceramic nanofibers, cellulose nanofibers, recycled products obtainableby heat treating carbon fiber that has been used or has become a wastematerial, and the like.

<Dispersion Liquid Composition>

The dispersion liquid composition according to the present invention isobtained by uniformly dispersing the powder composition by using aliquid reactive dispersing medium and/or a dispersing medium containinga thermoplastic polymer (also abbreviated as “thermoplastic polymer forthe dispersing medium”) having a deflection temperature under load or amelting point lower than that of the thermoplastic polymer used in thepowder composition, has conditions that a thermal conductive infinitecluster exhibiting a thermal conductivity of 1 to 35 W/mK is formed anda concentration of the thermal conductive filler is equal to or morethan a percolation threshold, and is excellent in segregation stability.

Since the vicinity of the high thermal conductive filler particles iscovered with fine organic polymer particles having a low specificgravity, there are advantages in that sedimentation due to a differencein specific gravity or separation due to strong aggregation of fillerparticles hardly occurs in the dispersion liquid, and workability isexcellent. There is no concern that the dispersion liquid composition isseparated at a temperature at the time of molding, cast molding, orpotting. The dispersion liquid composition is not separated at the sametemperature as described above for 1 hour or longer, and if beingseparated, it becomes uniform by simple stirring.

The dispersion liquid composition according to the present inventioncontains, with respect to 100 parts be weight of the powder composition,a reactive dispersing medium and/or a dispersing medium containing athermoplastic polymer for the dispersing medium in an amount of 25 to250 parts by weight (corresponding to 80 to 25 wt % in terms of thepowder composition concentration), preferably in an amount of 66 to 200parts by weight (corresponding to 60 to 30 wt % in terms of the powdercomposition concentration). Similarly to the powder composition, thedispersion liquid composition can also appropriately contain, asnecessary, the aforementioned additive, reinforcing agent, and/orfiller, and compatibilizer which are well known.

The dispersion liquid composition according to the present invention isnecessary to have fluidity at the time of cast molding or potting, andthe fluidity (viscosity) at that time can be measured by a rotationalviscometer and a capillary viscometer (also referred to a capillaryrheometer). The rotational viscometer employs a method of putting acylindrical rotor in a sample to obtain a viscosity from the rotationalspeed and torque thereof, and the capillary viscometer employs a methodof allowing a sample to flow into a thin nozzle to obtain a viscosityfrom a difference in pressure between both ends of the nozzle. Thedispersion liquid composition according to the present invention hasfluidity in which a viscosity in a rotational viscometer is 100 mPa·s ormore and a viscosity in a capillary viscometer is 300 Pa·s or less, andthe viscosity in the rotational viscometer and the viscosity in thecapillary viscometer are preferably 200 mPa·s or more and 250 Pa·s orless and more preferably 300 mPa·s or more and 200 Pa·s or less,respectively. The reason why the rotational viscometer is used for thelower limit and the capillary viscometer is used for the upper limit isthat, when fluidity is too high, the outflow quantity in the capillaryviscometer becomes too large so that fluidity cannot be measured, andwhen fluidity is too low, the rotation axis of the rotational viscometerslips so that accurate fluidity cannot be measured. With the viscosityin a range that can be measured by the rotational viscometer, loading(potting) of a resin by potting into a mold can be conducted, and in theviscosity in a range that can be measured by the capillary viscometer,injection into a mold by pressurization such as injection molding can beconducted.

When the curing calorific value of the liquid reactive dispersing mediumin the dispersion liquid composition according to the present inventionis 200 J/g or more, or the degree of cure thereof is 80% or more, thereis no concern that the thermoplastic polymer for the powder compositionis softened or melted at the time of molding, is deviated from thevicinity of the high thermal conductive filler particles to flow thethermoplastic polymer into a reactive dispersing medium phase, and thusthe thermal conductivity is decreased by the thermoplastic polymer beingunevenly distributed as large aggregates, and it is possible to providea resin material having a high mechanical strength.

For the measurement of the average particle sizes of the organic polymerparticles and the high thermal conductive filler particles of the rawmaterial, the powder composition, and the dispersion liquid composition,and the like, known methods such as a dynamic light scattering method, alaser diffraction method, an imaging method using an opticalmicroscope/electron microscope, and a gravity sedimentation method canbe used, and the level of delamination can be directly estimated by anoptical microscope or an electron microscope, or can be estimated bymeasuring the thermal conductivity, electrical conductivity, coefficientof thermal expansion, the mechanical characteristics, and the like ofmolded articles of the powder composition and the dispersion liquidcomposition. Further, a curing calorific value and a degree of cure ofthe dispersion liquid composition using a reactive dispersing medium canbe obtained using a differential scanning calorimeter (DSC).

Since the thermal conductive filler having a graphite-like structure hasa flat shape, when a dispersion liquid molded article is formed, thefiller tends to be oriented in the planar direction perpendicular to thepressure direction in such a manner that, particles are oriented alongthe planar direction and, in the side surface, particles are orientedalong the side surface. Therefore, the thermal conductivity and theelectrical conductivity in a specimen exhibit anisotropy of about 1.5 to5.5 times, but in a component with a fin structure, anisotropy isalleviated as a whole. In the present invention, a value of thermalconductivity is measured in a molded article (specimen) obtained bysubjecting the dispersion liquid composition to heat press molding. Avalue showing a thermal conductivity in the planar direction measured bya hot disc method is higher than a value showing a thermal conductivityin the thickness direction measured by a steady method. However, in acase where a resin is loaded in a mold and subjected to molding withoutpressurization, the thermal conductivity measured by the hot disc methodsometimes shows a lower value than that measured by the normal method,and the orientation of the filler greatly depends on whetherpressurization is performed at the time of loading and molding a resininto a mold, and anisotropy also depends thereon.

The dispersion liquid composition according to the present invention hasa condition that when a filler-loaded high thermal conductive materialdescribed later is obtained, in the hot disc method, a thermalconductive infinite cluster exhibiting a thermal conductivity of 1 to 35W/mK is formed, and this thermal conductivity is preferably 1.5 to 30W/mK, more preferably 2 to 25 W/mK, and further preferably 3 to 15 W/mK.When this thermal conductivity is 1 W/mK or more, heat generation of thecoil portion can be reduced, and when this thermal conductivity is 35W/mK or less, the viscosity of the dispersion liquid can be adjusted toa level that enables potting or cast molding under pressure to beperformed, which is preferable. In addition, the anisotropy of thethermal conductivity of the molded article can be alleviated by using aspherical filler in combination with a flat filler, and controllingmolding flow at the time of molding to make orientation random.

Incidentally, the term “infinite cluster” is based on the percolationtheory. Here, in general, the “percolation theory” is a theory on how anobject substance is connected in a system, and how the features of theconnection are reflected in the nature of the system. Specifically, whenthe filler particles are sufficiently brought into contact with oneanother to reach the percolation (penetration) threshold, the fillerparticles are aggregated to a concentration higher than or equal to aparticular concentration (threshold) of the thermal conductive filler toform a cluster in which the entire system stretches out (infinitecluster). Then, thermal conductivity is exhibited over the entiresystem. In order to exhibit thermal conductivity, thermal resistancebetween fillers is important in addition to contact between the fillerparticles as described above, and even if the contact is sufficient,when the thermal resistance at the interface is large, high thermalconductivity is not exhibited.

In the present invention, a thermal conductive filler-rich phase and athermal conductive filler-non-rich phase coexist in a material system, afiller of a thermal conductive filler-rich phase forms an infinitecluster so that a thermal conductivity is exhibited, and thus thethreshold is shifted to a low concentration side and as compared to acase where there is no filler-non-rich phase, the filler concentrationin the filler-rich phase increases and a high thermal conductivity inthe same filler concentration can be exhibited. Further, by thefiller-rich phase and the filler-non-rich phase forming a sea-islandstructure or an entangled network, there are no cracks at an interfacebetween the filler-rich phase and the filler-non-rich phase or aninterface between the filler and the resin, and a material beingexcellent in mechanical strength, thermal cycle properties, and the likecan be provided.

In the present aspect, whether or not the dispersion liquid compositionhas a condition that a thermal conductive infinite cluster is formed canbe predicted by measurement of physical property values such as athermal conductivity of a dispersion liquid composition molded article(filler-loaded high thermal conductive material) and microscopicobservation by a scanning electron microscope (SEM), an energydispersive X-ray analysis (EDX), and a transmission electron microscope(TEM).

[Reactive Dispersing Medium]

The reactive dispersing medium used in the present invention canuniformly disperse the aforementioned powder composition, forms acrosslinked polymer (cured product) by causing a chemical reaction withuse of heating, a catalyst, light, a curing agent, a curing accelerator,or the like, and becomes a continuous liquid phase when dispersing thepowder composition. As the reactive dispersing medium, an aromaticsubstituent containing the aforementioned uncured thermosetting resin ora known uncured thermosetting resin irrespective of existence ofcrystallinity can be used. Specific examples of the uncuredthermosetting resin include thermosetting resin precursors such as anepoxy resin, a silicone resin, a benzoxazine resin, an unsaturatedpolyester resin, a vinyl ester resin, a phenolic resin, a bismaleimideresin, a cyanate ester resin, an isocyanate ester resin, a polyimideresin and resin precursor mixtures thereof. Usually, the reactivedispersing medium is a liquid composition containing a reactive diluentof decreasing a viscosity of the thermosetting resin, a curing agent offorming a crosslinked polymer by reaction with the thermosetting resin,a catalyst of starting and/or promoting a curing reaction of thethermosetting resin, and/or a curing accelerator, and the like.

Regarding the reactive dispersing medium used in the present invention,in order to form a thermal conductive infinite cluster, it is necessaryto use an amount of 25 to 250 parts by weight with respect to 100 partsby weight of the powder composition, and when the viscosity of thedispersing medium is too high, the viscosity of the dispersion liquidcomposition increases so that a uniform composition having fluidity isnot obtainable. Therefore, the reactive dispersing medium is usually aliquid at room temperature, and the viscosity of the dispersing mediumat a temperature at the time of cast molding or potting is preferably200 mPa·s or less and more preferably 100 mPa·s or less.

As the epoxy resin, an epoxy resin having at least one epoxy group,preferably at least two epoxy groups, in one molecule is used. Specificexamples thereof include phenol-based epoxy resins such as a bisphenol Atype epoxy resin, a bisphenol F type epoxy resin, a bisphenol A-D typeepoxy resin, a novolac type epoxy resin, and a resol type epoxy resin;glycidyl esters such as polyhydric alcohol; epoxy compounds such as analicyclic epoxy resin, an amino type epoxy resin, and isocyanurate; andthe like. These are used singly or as a mixture thereof, and asnecessary, these are used by adding an epoxy-based reactive diluent, anepoxy resin curing agent, a catalyst, an epoxy resin curing accelerator,or the like.

The epoxy-based reactive diluent is to use for decreasing a viscosity ofa resin without impairing properties of an epoxy resin, examples thereofinclude alkyl monoglycidyl ether, alkyl phenol monoglycidyl ether, alkyldiglycidyl ether, and the like, and epoxy-based reactive diluents whichare usually used can be used.

The epoxy resin curing agent can form a crosslinked polymer by reactionwith an epoxy resin, and a novolac type and/or resol type phenolic resincan be used singly or as a mixture of two or more kinds thereof.Examples of an epoxy resin curing agent other than the phenolic resininclude amine-based curing agents such as triethylenetetramine anddiaminodiphenylmethane; acid anhydride-based curing agents such asmethyltetrahydrophthalic acid; a benzoxazine resin; imidazole;dicyandiamine; and the like, but the epoxy resin curing agent is notlimited thereto.

A mixing ratio of the epoxy resin and the epoxy resin curing agent isnot particularly problematic as long as it is a range that is usuallyused, a mixing ratio of the epoxy group and the epoxy resin curing agentin the whole epoxy resin is not particularly problematic as long as itis a range that is usually used, and an equivalence ratio of the epoxygroup in the whole epoxy resin and the functional group reacting withthe epoxy group in the whole epoxy resin curing agent is preferably 0.1to 2.0 and more preferably 0.5 to 1.3. With a value in theabove-described range, curing performance, thermal resistance, and thelike are sufficiently ensured, which is preferable.

The catalyst and/or curing accelerator for the epoxy resin is notparticularly limited as long as it is usually used as the catalystand/or curing accelerator for the epoxy resin, and they can be usedsingly or as a mixture of two or more kinds thereof. Examples of such acatalyst and/or curing accelerator include imidazoles such as2-methylimidazole and 2-phenylimidazole; amines such as tributylamine,2,4,6-tris(dimethylaminomethyl)phenol, and1,8-diazabicyclo(5,4,0)undecene-7; phosphororganic compounds such astriphenylphosphine; and the like, but the catalyst and/or curingaccelerator is not limited thereto. The used amount of such a catalystand/or curing accelerator is selected to be usually in a range of 0.01to 10 parts by weight and preferably in a range of 0.1 to 5 parts byweight with respect to 100 parts by weight of the epoxy resin. When theused amount of the curing accelerator is 0.01 part by weight or morewith respect to 100 parts by weight of the epoxy resin, a sufficientcatalyst or curing promotion effect is obtainable. In addition, when theused amount is 10 parts by weight or less, occurrence of adverse effectssuch as a decrease in water resistance/thermal resistance, a decrease inmoldability, and a decrease in physical properties of a cured product isprevented and this used amount is also preferred in economic terms.

The silicone resin is not particularly limited and a known siliconeresin can be used. Examples thereof include alkyl polysiloxanes such asdimethylpolysiloxane and methylphenyl polysiloxane; those which areobtained by adding an alkenyl group, a silanol group, a hydroxy group, acarboxyl group, and the like of those components; modified siliconeresins added with epoxy, acryl, urethane, and the like; and the like,and these can be used singly or as a mixture of two or more kindsthereof. Among these, modified silicone resins that can react with otherresins and in which a decrease in mechanical characteristics is smallare particularly preferred. Low-viscosity types can also be used as areactive diluent.

As the benzoxazine resin, known benzoxazine including the aforementionedbenzoxazine that is used in the powder composition and is a powder atnormal temperature can be used, but benzoxazine that can decrease aviscosity of the dispersion liquid composition and has a melting pointof 50° C. or lower, for example, Fa type benzoxazine manufactured bySHIKOKU CHEMICALS CORPORATION, and the like are preferred. As a curingaccelerator for the benzoxazine resin, known curing accelerators such asan epoxy resin, a phenolic resin, an imidazole catalyst, and an acidcatalyst can be used.

The unsaturated polyester resin is produced by diluting and dissolving areactive monomer mainly such as styrene in an unsaturated polyester,which is produced by polycondensation of an acid (saturated dibasicacid/unsaturated dibasic acid) of a main raw material and glycol, andknown unsaturated polyester resins can be used without particularlimitation. Further, the vinyl ester resin is produced by diluting anddissolving a reactive monomer mainly such as styrene in a vinyl ester,which is produced by addition reaction of an epoxy resin and a(meth)acrylic acid, and known vinyl ester resins can be used withoutparticular limitation.

The phenolic resin is one of thermosetting resins obtained bycondensation polymerization of phenol and formaldehyde under an acidcatalyst or an alkali catalyst. By using the acid catalyst, athermoplastic resin that is called novolac resin is obtained, but sincethe novolac resin itself is not cured even by heating, in the case ofcuring the novolac resin alone for use, it is necessary to use a curingagent such as hexamethylenetetramine. When synthesis is performed underan alkali catalyst, a resol resin is obtained. Since the resol resin hasan autoreactive functional group, the resol resin can be cured withoutany change by heating. Further, as mentioned above, the resol resin canbe used as a curing agent for an epoxy resin or a benzoxazine resin.

The bismaleimide resin is not particularly limited as long as it is aresin having maleimide groups at both ends of the molecule chain, butfurther, a resin having a phenyl group is preferred. Specific examplesthereof include N,N′-(4,4′-diphenylmethane)bismaleimide,bis(3-ethyl-5-methyl-4-maleimide phenyl)methane, 2,2-bis[4-(4-maleimidephenoxy) phenyl] propane, m-phenylene bismaleimide, p-phenylenebismaleimide, 4-methyl-1,3-phenylene bismaleimide, N,N′-ethylenedimaleimide, N,N′-hexamethylene dimaleimide, and the like, and these canbe used singly or in combination of two or more kinds thereof.

The cyanate ester resin is a compound having two or more of cyanategroup-OCN (cyanate ester) in the molecule, the isocyanate ester resin isa compound having two or more of isocyanate group-N═CO in the molecule,and known compounds can be used. In general, a compound having ahydroxyl group is used for a curing agent.

As the polyimide resin, there are mentioned one which is obtained by twostages in which tetracarboxylic dianhydride and diamine serving as rawmaterials are polymerized in equal moles to obtain polyamide acid(polyamic acid) which is a polyimide precursor, and thendehydration/cyclization (imidization) reactions are advanced by heatingor using a catalyst and one which is obtained by one stage in whichtetracarboxylic dianhydride and diisocyanate ester are reacted to eachother, and known polyimide resins can be used.

Requirements with respect to a cast molding resin and a potting materialfor preventing heat generation of the coil portion are diverse, asmentioned above, such as thermal conductivity, fluidity (viscosity),thermal resistance, mechanical strength, elasticity (toughness), andthermal cycle properties. Therefore, among the aforementionedthermosetting resins, as the reactive dispersing medium, a thermosettingresin configured by a benzoxazine resin and/or a phenol-based epoxyresin, and a modified silicone resin and/or an epoxy-based reactivediluent is preferred. The benzoxazine resin can provide thermalresistance, a mechanical strength, and the like and becomes a curingaccelerator for a phenol-based epoxy resin, and the phenol-based epoxyresin is an epoxy resin having a phenol structure, provides thermalresistance and a mechanical strength, and has favorable compatibilitywith benzoxazine. Since various grades thereof are commerciallyavailable, it is easy to cope with diverse physical propertyrequirements. The modified silicone resin is suitable for provision ofthermal resistance, elasticity (toughness), and the like, and theepoxy-based reactive diluent contributes to a decrease in viscosity,increases the concentration of the high thermal conductive filler tocontribute to an increase in thermal conductivity, and is necessary as acomponent of an epoxy-based dispersing medium.

Regarding the ratio of each of the thermosetting resins with respect to100 parts by weight of the reactive dispersing medium, the ratio of thebenzoxazine resin is preferably 0 to 60 parts by weight and morepreferably 5 to 40 parts by weight, the ratio of the phenol-based epoxyresin is preferably 5 to 60 parts by weight and more preferably 10 to 40parts by weight, the ratio of the modified silicone resin is preferably0 to 50 parts by weight and more preferably 5 to 30 parts by weight, andthe ratio of the epoxy-based reactive diluent is preferably 5 to 50parts by weight and more preferably 10 to 30 parts by weight.

In production of the reactive dispersing medium, although notparticularly limited, a mixing machine equipped with a stirrer that isgenerally known and is suitable for a liquid substance can be used, andfor uniform mixing, defoaming promotion, and the like, as necessary,mixing can be performed by heating and under vacuum. Further, in thesereactive dispersing media, as necessary, similarly to theabove-described catalyst, curing agent, and/or curing accelerator, orpowder composition, as necessary, known additives, reinforcing agentsand/or high thermal conductive fillers, compatibilizers, thermoplasticpolymers, and the like can be appropriately used.

[Thermoplastic Polymer for Dispersing Medium]

The melting point of the thermoplastic polymer for the dispersing mediumused in the present invention is preferably 100° C. or higher. Further,as long as the deflection temperature under load or the melting point islower than that of the thermoplastic polymer for the powder compositionby preferably 5 to 150° C., more preferably 10 to 100° C., and furtherpreferably 20 to 50° C., known thermoplastic polymers can be usedwithout particular limitation. When a difference in the deflectiontemperature under load or the melting point therebetween is 5° C. ormore, the thermoplastic polymer for the dispersing medium is fluidizedwithout the thermoplastic polymer for the powder composition beingdissolved or melted, so that the dispersion liquid composition can befluidized. In addition, if the difference thereof is 150° C. or less,for example, the melting point of the thermoplastic polymer for thepowder composition is 300° C., the melting point of the thermoplasticpolymer for the dispersing medium is 150° C. or higher, and a dispersionliquid composition molded article in which thermal resistance,durability, and the like are maintained can be obtained when thethermoplastic polymer for the dispersing medium is solidified, so thatthe effect of the present invention can be sufficiently exhibited.

As the thermoplastic polymer for the dispersing medium, theaforementioned thermoplastic polymer used as the organic polymerparticles is exemplified. Examples thereof include general-purposeresins such as polyethylene, polypropylene, polystyrene,acrylonitrile/styrene resin, acrylonitrile/butadiene/styrene resin,methacrylic resin, and vinyl chloride; general-purpose engineeringresins such as polyamide, polyacetal, polybutylene terephthalate,polyethylene terephthalate, polymethylpentene, and polycarbonate; superengineering resins such as polyphenylene sulfide, polyether etherketone, polyether imide, polyarylate, polysulfone, polyether sulfone,and polyamide; and the like; and mixtures thereof, but the thermoplasticpolymer for the dispersing medium is not limited thereto.

In the thermoplastic polymer for the dispersing medium, similarly to thepowder composition, as necessary, known additives, reinforcing agentsand/or fillers, compatibilizers, and thermosetting resins can beappropriately used.

<Method for Producing Dispersion Liquid Composition>

According to another aspect of the present invention, there is alsoprovided a method for producing a dispersion liquid composition which isexcellent in segregation stability. The production method includes astep (1) of obtaining a powder composition, which contains organicpolymer particles containing thermoplastic polymer particles, and highthermal conductive filler particles which contain filler particleshaving a graphite-like structure, by pulverizing 5 to 70 parts by weightof the organic polymer particles and 30 to 95 parts by weight of thehigh thermal conductive filler particles with respect to 100 parts byweight of the total amount of these components by using a pulverizingmachine, which performs grinding with frictional force or impact force,to cause delamination or cohesive failure while maintaining an averageplanar particle size of the filler particles having a graphite-likestructure, in the powder composition, the vicinity of the high thermalconductive filler particles being covered with the micronized organicpolymer particles and the covered particles being uniformly dispersed;and

a step (2) of uniformly dispersing the powder composition using 25 to250 parts by weight of a reactive dispersing medium and/or a dispersingmedium containing a thermoplastic polymer having a deflectiontemperature under load or a melting point lower than that of thethermoplastic polymer particles used in the powder composition withrespect to 100 parts by weight of the powder composition to prepare adispersion liquid composition having conditions that a thermalconductive infinite cluster exhibiting a thermal conductivity of 1 to 35W/mK is formed and a concentration of the high thermal conductive filleris equal to or more than a percolation threshold.

In the steps (1) and (2) in the method for producing a dispersion liquidcomposition, the aforementioned method in the dispersion liquidcomposition is appropriately employed.

When the powder composition is dispersed by a dispersing medium, inorder to perform uniform mixing, in addition to the mixing machinedescribed in the above description (the method for preparing a powdercomposition) and other machines, a known stirrer suitable for adispersing medium to be used, such as a known kneading machine used formelting and dispersing such as a disperser, a kneader, and asingle-screw and twin-screw extruder, can be used without no limitation,but it is not preferable to use a pulverizing machine by which the highthermal conductive filler in the powder composition is finely ground,such as a j et mill or an impact mill. In dispersing, it is necessary touniformly disperse the powder composition not to mix with bubbles, andin order to remove air contained in the dispersion liquid compositionand bubbles to be mixed during mixing/dispersing, it is preferable toperform the dispersing under reduced pressure or under vacuum.

The dispersing time is preferably 10 to 600 minutes and more preferably20 to 180 minutes. When the dispersing time is 10 minutes or longer, thepowder composition can be sufficiently dispersed, and when thedispersing time is 600 minutes or shorter, the dispersing is efficient.The dispersing temperature is, in the case of using a reactivedispersing medium as the dispersing medium, a temperature at which thereactive dispersing medium does not cause the chemical reaction, isusually 150° C. or lower and preferably 100° C. or lower, and thedispersing temperature is, in the case of using a thermoplastic polymerfor the dispersing medium, a temperature that is equal to or higher thanthe deflection temperature under load or the melting point of thethermoplastic polymer for the dispersing medium and is equal to or lowerthan the deflection temperature under load or the melting point of thethermoplastic polymer particles for the powder composition. When thedispersing temperature is equal to or higher than the deflectiontemperature under load or the melting point of the thermoplasticpolymer, the powder composition can be uniformly dispersed. In addition,when the dispersing temperature is equal to or lower than the deflectiontemperature under load or the melting point of the thermoplastic polymerparticles for the powder composition, the thermoplastic polymerparticles for the powder composition is not softened or melted at thetime of dispersing but can remain in the vicinity of the high thermalconductive filler particles. Further, when the thermoplastic polymer forthe dispersing medium is a powder, the thermoplastic polymer for thedispersing medium can be mixed at the time of producing the powdercomposition, and when the thermoplastic polymer for the dispersingmedium is a pellet, the thermoplastic polymer for the dispersing mediumcan be used by being melted and mixed with an extruder at the time ofmolding at a temperature equal to or lower than the melting point of thethermoplastic polymer for the powder composition, and a dispersionliquid composition master batch is produced in advance and can also beused as a raw material at the time of molding.

<Filler-Loaded High Thermal Conductive Material>

According to still another aspect of the present invention, there isalso provided a filler-loaded high thermal conductive material. Thefiller-loaded high thermal conductive material is formed by uniformlydispersing a powder composition, which contains organic polymerparticles containing thermoplastic polymer particles, and high thermalconductive filler particles which contain filler particles having agraphite-like structure and is obtained by pulverizing 5 to 70 parts byweight of the organic polymer particles and 30 to 95 parts by weight ofthe high thermal conductive filler particles with respect to 100 partsby weight of the total amount of these components by using a pulverizingmachine, which performs grinding with frictional force or impact force,to cause delamination or cohesive failure while maintaining an averageplanar particle size of the filler particles having a graphite-likestructure, in the powder composition, the vicinity of the high thermalconductive filler particles being covered with the micronized organicpolymer particles and the covered particles being uniformly dispersed,using 25 to 250 parts by weight of a liquid reactive dispersing mediumand/or a dispersing medium containing a thermoplastic polymer having adeflection temperature under load or a melting point lower than that ofthe thermoplastic polymer used in the powder composition with respect to100 parts by weight of the powder composition, and by causing adispersion liquid composition having conditions that a thermalconductive infinite cluster exhibiting a thermal conductivity of 1 to 35W/mK is formed and a concentration of the high thermal conductive filleris equal to or more than a percolation threshold to react under acondition that the reactive dispersing medium forms a crosslinkedpolymer, and/or to be fluidized at a temperature that is equal to orlower than a deflection temperature under load or a melting point of thethermoplastic polymer particles used in the powder composition and isequal to or higher than a deflection temperature under load or a meltingpoint of the thermoplastic polymer used in the dispersing medium, thento be molded by heating at a pressure of 0 to 1000 kgf/cm² and at atemperature equal to or higher than a deflection temperature under loador a melting point of the thermoplastic polymer particles used in thepowder composition, and cooled and solidified.

In the powder composition, the dispersing medium, and the dispersionliquid composition in the filler-loaded high thermal conductivematerial, embodiments described in each section are appropriatelyapplied.

The condition that the reactive dispersing medium forms a crosslinkedpolymer varies depending on the type of the reactive dispersing mediumto be used, the heating temperature, or use of a catalyst, light, acuring agent, and a curing accelerator, and is appropriately determinedaccording to the purpose of use/use application. Usually, the dispersionliquid is loaded in a mold, appropriately controlled to be cured usingthe aforementioned means at room temperature to a reaction (curing)temperature equal to or lower than the deflection temperature under loador the melting point of the organic polymer particles used in the powdercomposition, and then heated and molded. The final degree of cure of thereaction is preferably 80% or more. The reason for this is that, whenthe degree of cure is 80% or more, the contact between the thermalconductive fillers can become dense in the subsequent heating andmolding and an effective thermal conduction path can be formed. Further,a method of fluidizing the thermoplastic polymer for the dispersingmedium is performed at a temperature that is equal to or lower than thedeflection temperature under load or the melting point of thethermoplastic polymer particles used in the powder composition and isequal to or higher than the deflection temperature under load or themelting point of the thermoplastic polymer for the dispersing medium,and usually, the thermoplastic polymer for the dispersing medium iskneaded and loaded in a mold by an extruder or the like, and then heatedand molded.

In the heating and molding, the thermoplastic polymer is molded byheating at a temperature equal to or higher than the deflectiontemperature under load or the melting point of the thermoplastic polymerparticles used in the powder composition at a pressured of 0 to 1000kgf/cm², cooled, and solidified. As the molding method, known moldingmethods such as injection molding, extrusion molding, hollow molding,compression molding, transfer molding, powder molding, calender molding,and thermoforming can be used without limitation, and the molding methodcan be executed by using means respectively suitable for thethermoplastic resin and the thermosetting resin. As the common subjectmatter, a resin is melted by being applied with heat, shaped, cooled,and solidified. During the molding process, as necessary, the moldingcan be performed under reduced pressure or under vacuum.

Since the filler-loaded high thermal conductive material of the presentinvention is configured as described above, at the stage in which thereactive dispersing medium used as the dispersing medium is crosslinkedand/or the stage in which the thermoplastic polymer used as thedispersing medium is fluidized, the initial concentration of the highthermal conductive filler, which is a constituent element of the powdercomposition, in the powder composition is maintained, then at the stagein which the thermoplastic polymer particles, which are otherconstituent elements of the powder composition, in the organic polymerparticles are heated to a temperature that is equal to or higher thanthe deflection temperature under load or the melting point, micronizedthermoplastic polymer particles are softened and/or melted, then at thestage of cooling/solidifying, the filler-rich phase and thefiller-non-rich phase are formed, and an advanced thermal conductionpath in which the high thermal conductive filler is efficientlyconnected is formed in the filler-rich phase.

A constituent of the filler-rich phase is determined by affinity of anorganic material component (an organic polymer, a reactive dispersingmedium, a thermoplastic resin for a dispersing medium, or the like) withrespect to the filler and the migratory property of the organic materialcomponent to the filler, and the former mainly depends on surface freeenergy and the latter mainly depends on molecular weight. The surfacefree energy (γ) can be obtained by measuring a contact angle of liquiddroplet on the solid surface, and known components of two or moreliquids and an actual measurement value are assigned to the theoreticalformula to solve the theoretical formula so that they can be resolvedinto a dispersion component (γ^(d)) and a polar component (γ^(p)). Forexample, in hexagonal boron nitride, γ^(d)=38.3 mJ/m² and γ^(p)=15.3mJ/m², in a PPS resin, γ^(d)=45.2 mJ/m² and γ^(p)=0.1 mJ./m², in nylon6, γ^(d)=27.5 mJ/m² and γ^(p)=26.2 mJ/m², and in polybenzoxazine,γ^(d)=38.7 mJ/m² and γ^(p)=3.0 mJ/m². By dividing the surface freeenergy into the dispersion component and the polar component, whichcomponent effectively contributes to affinity is found.

The affinity between the filler and the organic material becomes higheras the difference of the surface free energies between both componentsare minimized, and this is coincident well with empirical rules thatsimilar components are dissolved well and attached well to each other.For example, in the system of hexagonal boron nitride-PPS resin-nylon 6,the polar component term of the surface free energy is dominant, thefiller-rich phase has hexagonal boron nitride and nylon 6 in which adifference in surface free energy between them becomes a minimum valueas main constituents, and regarding the filler-non-rich phase, a PPSresin is a main constituent. In a case where the thermoplastic resinbecomes a filler-non-rich phase, aggregation occurs at the time ofmelting (and/or softening)-cooling-solidifying and the particle sizeincreases in some cases, but since the thermoplastic resin usuallybecomes an island part in the sea-island structure, this does not exertsignificant influence on thermal conductivity, electricalcharacteristics, and mechanical characteristics. Since the reactivedispersing medium usually has a small molecular weight, the migratoryproperty to the vicinity of the filler is high, and in a case where theaffinity with the filler is high, the reactive dispersing medium isparticularly easy to become a filler-rich phase. However, the surfacefree energy changes by the filler being surface-treated or the surfaceof the filler being oxidized, and the affinity with the organic materialcomponent changes. Further, by reaction of the reactive dispersingmedium (for example, ring-opening of an oxazine ring or an epoxy group),a polar functional group is generated and the affinity to the fillerchanges, and thus it is necessary to take these points of view intoconsideration.

By emergence of the high thermal conductive filler-rich phase asmentioned above, an advanced and effective thermal conduction path isformed, and even when the percolation threshold of the thermalconductivity is decreased and the filler concentration is low, a highthermal conductivity is exhibited. The polymer microstructure(morphology) of each of these filler particle phase, organic polymerphase, and dispersing medium phase can be measured by microscopicobservation through SEM, TEM, and EDX analyses of a material (moldedarticle).

In order to obtain excellent properties such as a thermal conductivity,a bending strength, a flexural modulus of elasticity, and impactresistance, it is important that the filler-rich phase and thefiller-non-rich phase coexist in a uniform state, a thermal conductiveinfinite cluster of the filler in the filler-rich phase is formed bysoftening or melting, cooling, and solidifying. In particular, when areactive dispersing medium is used as the dispersing medium, in thecondition that a crosslinked polymer is formed, it is important that thedegree of cure of the reactive dispersing medium is increased and thethermoplastic polymer used in the powder composition is softened ormelted.

<Method for Producing Filler-Loaded High Thermal Conductive Material>

According to still another aspect of the present invention, there isalso provided a method for producing a filler-loaded high thermalconductive material. The production method includes a step (1) ofobtaining a powder composition, which contains organic polymer particlescontaining thermoplastic polymer particles, and high thermal conductivefiller particles which contain filler particles having a graphite-likestructure, by pulverizing 5 to 70 parts by weight of the organic polymerparticles and 30 to 95 parts by weight of the high thermal conductivefiller particles with respect to 100 parts by weight of the total amountof these components by using a pulverizing machine, which performsgrinding with frictional force or impact force, to cause delamination orcohesive failure while maintaining an average planar particle size ofthe filler particles having a graphite-like structure, in the powdercomposition, the vicinity of the high thermal conductive fillerparticles being covered with the micronized organic polymer particlesand the covered particles being uniformly dispersed;

a step (2) of uniformly dispersing the powder composition using 25 to250 parts by weight of a liquid reactive dispersing medium and/or adispersing medium containing a thermoplastic polymer having a deflectiontemperature under load or a melting point lower than that of thethermoplastic polymer particles used in the powder composition withrespect to 100 parts by weight of the powder composition to prepare adispersion liquid composition having conditions that a thermalconductive infinite cluster exhibiting a thermal conductivity of 1 to 35W/mK is formed and a concentration of the high thermal conductive fillerparticles is equal to or more than a percolation threshold;

a crosslinking step (3) of allowing the dispersion liquid composition toreact under a condition that the reactive dispersing medium forms acrosslinked polymer; and/or a fluidizing step (4) of fluidizing thethermoplastic polymer used in the dispersing medium at a temperaturethat is equal to or lower than a deflection temperature under load or amelting point of the thermoplastic polymer used in the powdercomposition and is equal to or higher than a deflection temperatureunder load or a melting point of the thermoplastic polymer used in thedispersing medium;

a step (5) of molding by heating the material formed in the crosslinkingstep (3) and/or the fluidizing step (4) at a pressure of 0 to 1000kgf/cm² and at a temperature equal to or higher than a deflectiontemperature under load or a melting point of the organic polymerparticles; and

a step (6) of cooling and solidifying the material formed in the step(5).

In the steps (1), (2), (3), (4), (5), and (6) in the method forproducing a filler-loaded high thermal conductive material, the methodpresented in the section of the filler-loaded high thermal conductivematerial is appropriately employed.

The condition that the reactive dispersing medium forms a crosslinkedpolymer can be obtained by measuring a curing exothermic behavior byusing a thermogravimetric/differential thermal (TG/DTA) device and adifferential scanning calorimeter (DSC). Regarding the curingtemperature and the curing time, the optimum condition can be determinedwhile an exothermic peak temperature when the curing temperature and thecuring time are measured under a certain temperature increase rate isused as an indicator. In a case where a thermogravimetric decrease at alow temperature during TG analysis is significant, not only a decreasein reaction product occurs but also air bubbles based on volatilecomponents in the cured product are included, so that a decrease inphysical properties occurs, which is not preferable. At this time, sucha situation can be prevented by defoaming before curing under reducedpressure or decreasing a curing temperature by concurrently using acatalyst, a curing accelerator, or the like. It is preferable that,during the powder composition exists in a solidified form, thedispersion liquid composition is subjected to cast molding to cure thereactive dispersing medium, and as necessary deforming under reducedpressure, is heated to a temperature equal to or higher than thedeflection temperature under load or the melting point of thethermoplastic polymer for the powder composition and then under pressureto be molded.

In a case where the thermoplastic polymer is used as the dispersingmedium, it is preferable that, during the thermoplastic polymer for thepowder composition exists in a solidified form, the dispersion liquidcomposition is heated at a temperature equal to or higher than thedeflection temperature under load or the melting point of thethermoplastic polymer for the dispersing medium to be fluidized and castmolded in a mold, and as necessary, is heated to a temperature equal toor higher than the deflection temperature under load or the meltingpoint of the thermoplastic polymer for the powder composition underreduced pressure for removing air bubbles, and then under pressure to bemolded.

The present invention is configured as mentioned above, so that theknown molding method and apparatus described in the section of thefiller-loaded high thermal conductive material can be used. In the caseof utilizing injection molding using a thermoplastic polymer as adispersing medium, when a raw material is supplied while the dispersionliquid composition is formed into a tablet or pellet in a state wherethe powder composition maintains the morphology of thermal conductivity,it is easy to supply the raw material to an extruder.

<Molded Article Obtained by Using Filler-Loaded High Thermal ConductiveMaterial>

According to an embodiment of the present invention, there is alsoprovided a molded article containing the above-described filler-loadedhigh thermal conductive material or a filler-loaded high thermalconductive material produced by the above-described production method,the molded article being used as a high thermal conductive/heatdissipation component and including a sheet, film, or the like.

In production of the molded article, the molding method described in thesection of the method for producing a filler-loaded high thermalconductive material can be appropriately applied, and by using a mold toobtain a desired shape, a molded article having a shape according to useapplication can be easily obtained. By using different materials asmolding raw materials, a molded article having a multi-layer structureor a gradient structure, for example, an integral molded article havinga two-layer structure in which an insulating dispersion liquidcomposition is injected to a coil portion of a stator or a reactornecessary for insulating properties and an exterior resin formed fromconductive dispersion liquid composition is integrally molded to theoutside thereof, or having a gradient structure in which gradientmaterials each having a different concentration of the high thermalconductive filler are integrally molded is obtained, so that heatgenerated from the coil portion and the core portion can be efficientlyremoved.

At this time, it is possible to use known method such as a method inwhich a stator or a reactor is fixed into a mold, an insulatingdispersion liquid composition (interior resin) is injected to a coilportion, after curing by heating, a conductive dispersion liquidcomposition that is an exterior resin is injected, and the compositionsare integrally molded at a temperature equal to or higher than adeflection temperature under load or a melting point of thethermoplastic polymer used in the solid component; a method in which anexterior resin is first molded, and then an interior resin is injectionmolded; and a method in which an exterior resin is separately molded,and then an exterior resin is fused to the interior resin. At this time,when the same polymer or a polymer having favorable compatibility isused as the thermoplastic polymer used in each of the exterior resin andthe interior resin, adhesiveness at the interface between the layers isenhanced, functional properties such as thermal conductivity anddurability such as mechanical characteristics and thermal cycles can beenhanced. Alternatively, the insulating properties of the coil aresufficiently secured, and the conductive dispersion liquid compositionis used in the interior resin and the exterior resin, so that a decreasein cost can be achieved.

In a preferred embodiment, it is preferable that in a molded articleobtained by laminating two layers, a thermal conductivity of one layerof the two layers is 3 to 35 W/mK and the one layer exhibits electricalconductivity having a surface electrical conductivity of 70 (Ωcm)⁻¹ orless, preferably 1 to 70 (Ωcm)⁻¹; whereas, a thermal conductivity of theother layer of the two layers is 1 to 25 W/mK and the other layerexhibits insulating properties having a surface electrical conductivityof 10⁻¹⁰ (Ωcm)⁻¹ or less. However, even if sufficient insulatingproperties are secured in a coil or the like, a semiconductor regionhaving a surface electrical conductivity of 0.1 (Ωcm)⁻¹ or less can beused. Further, when the electrical conductivity is 1 (Ωcm)⁻¹ or more,electromagnetic shielding properties are exhibited, and when theelectrical conductivity is 70 (Ωcm)⁻¹ or less, the viscosity of thedispersion liquid is decreased to enable the dispersion liquid to beinjected under pressure while insulating properties are exhibited, whichis preferable.

Since the filler-loaded high thermal conductive material and the moldedarticle according to the present invention are configured as mentionedabove, the present invention can exhibit properties inherent in theorganic polymer such as lightweight properties, designability, moldingprocessability, cutting processability, integral moldability, dimensionstability, and enhancement in physical properties according to useapplication while taking advantage of properties inherent in the highthermal conductive filler containing the filler having a graphite-likestructure to be used, is excellent in thermal conductivity, heatdissipation properties, electrical characteristics, thermal resistance,mechanical characteristics, thermal cycle properties, and the like, andcan meet various requirements for final products of electric/electronicequipment, rotating electrical machines, and the like. Other than themolded article, the filler-loaded high thermal conductive material canbe used for various use applications that take advantage of fluidity andhave a problem of heat dissipation, such as a sheet, an adhesive,grease, and a sealing material, and by packaging of electronic/electricdevices, it is possible to provide devices excellent in waterproofproperty, dust proof property, and the like.

The insulating material using ceramic filler particles or the like canbe used in copper foil parts of substrates of electronic/electricdevices necessary for insulating properties, parts being in contact withcoil portions of stators, reactors, inductors, transformers, or thelike, and a sealing material for substrates of power supplies or thelike, and the conductive material using graphite particles or the likecan be used in splitters, fins, housings, and the like which have a highthermal emittance and a high electrical conductivity and release thegenerated heat to the outside, and can be effectively used as amember/component used in the fields of automobiles, motorcycles,aircrafts, air conditioners, robots, drones, and the like which arerequired for weight saving, compactification, and the like.

A motor or a power generator relatively rotates a magnetic and a coil togenerate driving power or electric power, a stationary side is called astator, a rotation side is called a rotor, and the stator and the rotorcan also be moved in a horizontal direction with the same principle(linear motor). A reactor is a passive element using an inductor (thatcan accumulate energy in a magnetic field formed by flowing current,usually includes a coil, and is also frequently called a coil), and thereactor is used as components for converters or inverters.

In automobiles, 50 to 150 motors are used in various parts related tovariable engines or the like, related to vehicle bodies such as awindshield wiper, related to vehicle interiors such aselectricity-conducting power steering, for purifiers for power slidingdoor air or the like, and the like, a power generator for generatingpower is also used, as the type of motor, a DC blush-attached motor, aPWM-attached DC blush-attached motor, a brushless motor, a steppingmotor, and the like are mentioned, and the present invention can be usedin stators used therefor. In robots, a DC motor, a DC servomotor, an ACmotor, an induction motor, an AC servomotor, a linear motor, a steppingmotor, and the like are used, and the present invention can also be usedin stators used therefor.

In particular, in the case of using the present invention in a stator ofa motor and reactors of an inverter and a converter, the dispersionliquid composition using insulating filler particles such as ceramicscan be used as an interior cast molding resin for a coil portion of astator or a reactor, and the dispersion liquid composition usingconductive filler particles such as graphite can be used as an exteriorresin for a stator or a reactor. In the case of two-color molding boththe compositions, the interface between the both the composition can bestrongly bonded by the thermoplastic polymers having favorablecompatibility, so that an increase in thermal resistance at theinterface and a decrease in mechanical strength can be prevented.

Further, when a strong electromagnetic wave is applied to electronicequipment from the outside, a necessary current is induced to a circuit,an unintended operation occurs so that this unintended operation mayinhibit an original operation, which causes malfunction. In recentyears, electric/electronic equipment has been widely used in variousfields, and measures against noise have become important. Amember/component according to the present invention has less noise, andthus can be effectively utilized as EMC (electromagnetic interference)measures for noise prevention, and can be useful for malfunction or thelike of sensors that is concerned with widespread of automated drivingand IoT.

EXAMPLES

Hereinafter, the present invention will be described in detail by meansof Examples, Comparative Examples, Reference Examples, and ComparativeReference Examples, but the scope of the present invention is notintended to be limited to these. Incidentally, production and evaluationof raw materials, dispersion liquid compositions, and molded articleswere carried out as follows.

(1) Raw Materials

[Thermoplastic Polymer]

-   -   Polyphenylene sulfide (PPS) particles: W203A NATURAL        manufactured by KUREHA CORPORATION, white powder, linear form,        particle size 100 to 500 μm, specific gravity 1.35, melting        point 294° C. (DSC measurement), surface free energy (contact        angle measurement): dispersion component (γ^(d))=45.2 mJ/m² and        polar component (r)=0.1 mJ/m²    -   Polyamide (nylon 6) particles: manufactured by Ube Industries,        Ltd., white powder, average particle size 150 μm, melting point        223° C. (DSC measurement), surface free energy (contact angle        measurement): dispersion component (γ^(d))=27.5 mJ/m² and polar        component (γ^(p))=26.2 mJ/m²    -   Polypropylene (PP) particles: PP Powder PPW-5J manufactured by        SEISHIN ENTERPRISE Co., Ltd., white powder, average particle        size 5.6 μm, melting point 147° C. (DSC measurement), surface        free energy (contact angle measurement): dispersion component        (γ^(d))=36.4 mJ/m² and polar component (γ^(p))=0.2 mJ/m²

[High Thermal Conductive Filler]

-   -   Boron nitride: hexagonal BN nitride simple grain type UHP-2        manufactured by Showa Denko K.K., white powder, average particle        size 9 to 12 μm, bulk thermal conductivity 60 W/mK (anisotropic        filler: planar direction 200 W/mK; depth direction 60 W/mK),        surface free energy (contact angle measurement): dispersion        component (γ^(d))=38.3 mJ/m² and polar component (γP)=15.3 mJ/m²    -   Aluminum oxide: spherical alumina DAW-45 manufactured by Denka        Company Limited, average particle size 42.7 μm, thermal        conductivity 40 W/mK (isotropic filler)    -   Magnesium oxide: RF-98 manufactured by Ube Material Industries,        Ltd., white powder, average particle size 50.6 μm, thermal        conductivity 45 to 60 W/mK (isotropic filler)    -   Scale-like graphite: BF-40K manufactured by Chuetsu Graphite        Works Co., Ltd., scale-like black powder, average particle size        40 μm, bulk thermal conductivity 150 to 200 W/mK (anisotropic        filler: planar direction 200 to 600 W/mK, thickness direction 5        to 12 W/mK), surface free energy (contact angle measurement):        dispersion component (γ^(d))=44.4 mJ/m² and polar component        (γP)=4.2 mJ/m²    -   Graphite scraps: graphite scraps for electrodes manufactured by        Showa Denko K.K., particle size 10 to 300 μm (SEM observation)

[Thermosetting Resin]

-   -   P-d type benzoxazine resin: P-d type benzoxazine manufactured by        SHIKOKU CHEMICALS CORPORATION, pale yellow powder, particle size        0.01 to 0.1 mm (SEM observation), melting point 75° C., curing        exothermic peak temperature 242° C. (DSC measurement), curing        calorific value 239 J/g    -   F-a type benzoxazine resin: F-a type benzoxazine manufactured by        SHIKOKU CHEMICALS CORPORATION, pale yellow block, softening        point 30° C. (DSC measurement), curing exothermic peak        temperature 241° C. (DSC measurement), curing calorific value        220 J/g, surface free energy of cured product (contact angle        measurement): dispersion component (γ^(d))=38.7 mJ/m² and polar        component (γ^(p))=4.2 mJ/m²    -   Phenol-based epoxy resin: bisphenol F type liquid epoxy resin        EPICLON830 manufactured by DIC Corporation, epoxy equivalent 165        to 177 g/eq, transparent liquid, viscosity 3000 to 4000 mPa·s        (25° C.), specific gravity 1.19 (25° C.)    -   Epoxy-based reactive diluent: GLYCIROL ED-503G (chemical name        1,6-hexanediol diglycidyl) manufactured by ADEKA Corporation,        transparent liquid, epoxy equivalent 135 g/eq, viscosity 15        mPa·s (25° C.), specific gravity 1.08 (25° C.)    -   Epoxy-modified silicone resin: silicone resin having both ends        modified with epoxy X-22-163 manufactured by Shin-Etsu Chemical        Co., Ltd., epoxy equivalent 200 g/eq, transparent liquid,        viscosity 15 mm²/s (25° C.), specific gravity 1.00 (25° C.)    -   Amine-modified silicone resin: silicone resin having both ends        modified with amine X-22-161B manufactured by Shin-Etsu Chemical        Co., Ltd., functional group equivalent 1500 g/eq, transparent        liquid, viscosity 55 mm²/s (25° C.), specific gravity 0.97 (25°        C.)    -   Catalyst: imidazole-based catalyst 2E4MZ-A manufactured by        SHIKOKU CHEMICALS CORPORATION, white powder

(2) Measurement of Physical Properties of Dispersion Liquid Composition

[Fluidity Test]

-   -   Viscosity (mPa·s) by rotational viscometer: A viscosity was        measured according to JIS K7117-1 (1999) by using a digital        (rotational) viscometer DV2T (manufactured by Brookfield) by the        following Equation (1) while changing the rotational speed of a        spindle at 100° C., and in a relation between a viscosity        (mPa·s) and a shear velocity (1/s), the viscosity after the        numerical value was stable was read and obtained.

η=Ka×(T/ω)  (1)

Here, η: viscosity (mPa·s) of the dispersing medium and the dispersionliquid, Ka: apparatus constant (rad/cm²), ω: angular velocity (rad/s),and T: torque (10⁻⁷ N·m) acting on the spindle. Viscosity (mP·s) bycapillary viscometer: A thermal fluidity was evaluated using a capillaryrheometer (Flowtester (CFT-500 type) manufactured by SHIMADZUCORPORATION. 2.5 to 3.5 g of a sample was loaded in a cylinder having across-sectional area of 1 cm² by using a nozzle having a caliber of 1 mmand a length of 1 mm, a piston was inserted, and maintained for 2minutes at 170° C. in the case of the dispersing medium beingpolypropylene, 260° C. in the case of the dispersing medium being nylon,and 100° C. in the case of the dispersing medium being a thermosettingresin (reactive dispersing medium), a volume (Q) of the sample flowingout per unit time when being applied with a load of 50 to 500 kg wasobtained, and a shear velocity (Dω) and a viscosity (η) were obtained bythe following Equations (3) and (2), respectively. Since the viscosityincreases as the load increases but the dispersing medium is separatedwhen the load is low, the viscosity at a load of 300 kg was employed.

η=π×R ⁴ ×P/(8×L×Q)  (2)

Dω=4×Q/(π×R ³)  (3)

Here, η: viscosity (poise (1 cP=1 mPa·s)) of the dispersion liquid, Dω:shear velocity (1/s), R: nozzle radius (cm), P: load pressure (dyne/cm²(1 dyne=1.02 kgf)), L: nozzle length (cm), and Q: flow value (ml/s).

[Curing and Exothermic Test]

-   -   Curing exothermic peak temperature and calorific value: The        exothermic behaviors of the dispersing medium and the dispersion        liquid composition at a heating rate of 10° C./min under a        nitrogen atmosphere were measured using a differential scanning        calorimeter (DSC-60A Plus) (manufactured by SHIMADZU        CORPORATION) to obtain a curing exothermic peak temperature, a        calorific value (J/g), and a degree of cure (%), and the        obtained values were regarded as indicators of curing        temperatures of the dispersing medium and the dispersion liquid        composition.

[Measurement of Melting Point of Thermoplastic Polymer]

-   -   Melting point: The thermal behaviors of the powder composition,        the dispersing medium, and the dispersion liquid composition at        a heating rate of 10° C./min under a nitrogen atmosphere were        measured using the differential scanning calorimeter, a melting        point (° C.) of the thermoplastic polymer was obtained from the        endothermic peak temperature, and the existence of the        thermoplastic polymer was confirmed.

[Segregation Stability Test]

-   -   Segregation stability test of dispersion liquid using reactive        dispersing medium: 100 g of the dispersion liquid was weighed in        a plastic container having an inner diameter of 62 mm (interior        volume 140 ml) and left to stand still in a high-temperature        tank set to 100° C. for 8 hours, a volume percentage of an upper        separated layer (mainly the dispersing medium) was obtained, and        thus a separation degree (%) was obtained.    -   Segregation stability test of dispersion liquid using        thermoplastic polymer as dispersing medium: 5 g of the        dispersion liquid was weighed in a glass test tube having an        inner diameter of 12.5 mm (interior volume 15 ml) and left to        stand still in a high-temperature tank set to 160° C. in the        case of the dispersing medium being polypropylene and set to        250° C. in the case of the dispersing medium being nylon for 12        hours, a volume percentage of an upper separated layer (mainly        the dispersing medium) was obtained, and thus a separation        degree (%) was obtained.

(3) Physical Properties of Molded Article

[Measurement of Thermal Conductivity]

-   -   Measurement by hot disc method: The thermal conductivity was        measured using a thermal property analyzer of a hot disc method        (TPS2500S manufactured by Kyoto Electronics Manufacturing Co.,        Ltd.). The hot disc method takes consideration of making        measurement to the extent that heat generated from a hot disc        sensor is transferred to the interior of a specimen, and the        heat does not reach to the end of the specimen. Thus, the hot        disc method is to measure thermal conductivity (W/mK) in the        vicinity of the surface of a specimen to a certain depth. In the        case of an anisotropic material, the thermal conductivity in the        planar direction can be measured.    -   Measurement by temperature gradient method: A specimen was        sandwiched with aluminum blocks, one was heated from a ceramic        heater at a certain heat quantity and the other one was cooled        with water set at 25° C. to cause temperature gradient, and then        a thermal conductivity (W/mK) was calculated from a difference        in temperature between steady heat flow and specimen both ends.        In the case of an anisotropic material, the thermal conductivity        in the depth direction can be measured.

[Measurement of Electrical Conductivity]

-   -   The electrical conductivity ((Ωcm)⁻¹) at a surface and a        cross-section of the specimen was measured according to JIS        K7194 (1994) using a low resistivity meter Loresta GP        (four-point probe method) (manufactured by Mitsubishi Chemical        Analytech Co., Ltd.). The measurement range is 10⁻³ to 10⁷Ω and        the electrical conductivity of the conductive material can be        measured.    -   The electrical conductivity ((Ωcm)⁻¹) of the specimen was        measured according to JIS K6911 (1995) using a high resistivity        meter HIRESTA UX (manufactured by NIHON DENKEI CO., LTD.). The        measurement range is 10⁴ to 10¹⁴Ω and the electrical        conductivity of the insulating material can be measured.

[Thermal Resistance Test]

-   -   Measurement of decomposition temperature: A thermogravimetric        change from room temperature to 1000° C. at a heating rate of        10° C./min under a nitrogen atmosphere was measured by using        TG/DTA DTG-60 (manufactured by SHIMADZU CORPORATION), and a        temperature (° C.) when the weight is decreased by 10% was        regarded as 10% weight loss temperature and was used as an        indicator of thermal resistance.

[Bending Test]

-   -   Measurement of bending strength and flexural modulus of        elasticity: A molded article was cut to produce a measurement        sample having a size of 10 mm in width×4 mm in thickness×40 mm        in length, and a bending strength (MPa) and a flexural modulus        of elasticity (GPa) were measured according to JIS K7171 (2016)        by using a universal testing machine Autograph ABS-X (1 kN)        (manufactured by SHIMADZU CORPORATION).

[Impact Resistance Test]

-   -   Charpy impact test: A molded article was cut to produce a        measurement sample having a size of 80 mm in width×4 mm in        thickness×10 mm in length, and the Charpy impact value (kJ/m²)        was obtained according to JIS K7111-1 (2012) by using an impact        testing machine IT (manufactured by Toyo Seiki Seisaku-sho,        Ltd.).

(4) Measurement of Contact Angle and SEM/EDX Analysis

[Measurement of Contact Angle]

Two types of liquids (water and diiodomethane) having a known surfacefree energy (γ_(L)) were added dropwise onto a solid molded article, acontact angle (θ) was measured by using an automatic contact anglemeasurement apparatus DMe211 manufactured by Kyowa Interface ScienceCo., Ltd., and a dispersion force component (γ_(S) ^(d)) of the solidmolded article and a surface free energy of a polar component (γ_(S)^(p)) were obtained by the following equations.

W _(SL)=γ_(L)(1+θ)=2√(γ_(S) ^(d)γ_(L) ^(d))+2√(γ_(S) ^(p)γ_(L)^(p))  (4)

γ_(S)=γ_(S) ^(d)+γ_(S) ^(p)  (5)

[Measurement of SEM/EDX]

The molded article, which had been subjected to hub polishing inadvance, was subjected to SEM/EDX analysis by using a scanning electronmicroscope (SEM) JSM-IT100 manufactured by JEOL Ltd. under theconditions of sputter deposition (Pt (5 nm)) and an accelerating voltageof 10 kV.

Reference Examples 1 to 8 and Comparative Reference Examples 1 and 2:Preparation Examples of Powder Compositions

Filler particles having a graphite-like structure, other high thermalconductive filler particles, and organic polymer particles wereaccurately weighed in amounts presented in the following Table 1, wereintroduced into a magnetic pot of a desk type ball mill BM-10(manufactured by Seiwa Giken Co., Ltd.), and the contents werepulverized and mixed for 4 hours at room temperature by using magneticballs to thereby obtain a uniform powder composition. A part of theobtained powder composition was taken out and subjected to DSCmeasurement, and the melting point of the organic polymer particles wasobtained from an endothermic peak temperature. The obtained results arepresented in the following Table 1. Incidentally, among preparationexamples presented in Table 1, examples containing the organic polymerparticles were regarded as Reference Examples 1 to 8. In addition,regarding examples not containing organic polymer particles, onlycompositions were presented and these examples were regarded asComparative Reference Examples 1 and 2.

TABLE 1 Reference Example and Comparative Reference Example ReferenceReference Reference Reference Reference Reference Example 1 Example 2Example 3 Example 4 Example 5 Example 6 Filler particles havinggraphite-like structure Boron nitride (parts by weight) 80 60 60 60 0 0Scale-like graphite (parts by weight) 0 0 0 0 80 20 Graphite scraps(parts by weight) 0 0 0 0 0 60 Other high thermal conductive fillerparticles Magnesium oxide (parts by weight) 0 20 20 0 0 0 Aluminum oxide(parts by weight) 0 0 0 20 0 0 Organic polymer particles PPS resin(parts by weight) 20 20 16 20 20 20 Nylon 6 resin (parts be weight) 0 00 0 0 0 P-d type benzoxazine (parts by weight) 0 0 4 0 0 0 Powdercomposition Concentration (wt %) of high thermal conductive filler 80 8080 80 80 80 Concentration (wt %) of filler having graphite-likestructure 80 75 75 75 80 80 Melting point (° C.) of organic polymer 294294 75,294 294 294 294 Reference Example and Comparative ReferenceExample Comparative Comparative Reference Reference Reference ReferenceExample 7 Example 8 Example 1 Example 2 Filler particles havinggraphite-like structure Boron nitride (parts by weight) 0 80 100 0Scale-like graphite (parts by weight) 20 0 0 25 Graphite scraps (partsby weight) 60 0 0 75 Other high thermal conductive filler particlesMagnesium oxide (parts by weight) 0 0 0 0 Aluminum oxide (parts byweight) 0 0 0 0 Organic polymer particles PPS resin (parts by weight) 00 0 0 Nylon 6 resin (parts be weight) 20 20 0 0 P-d type benzoxazine(parts by weight) 0 0 0 0 Powder composition Concentration (wt %) ofhigh thermal conductive filler 80 80 100 100 Concentration (wt %) offiller having graphite-like structure 80 80 100 100 Melting point (° C.)of organic polymer 223 223 — —

Examples 1 to 9: Preparation Examples of Dispersion Liquid CompositionsUsing Reactive Dispersing Medium as Dispersing Medium

The dispersing media (the compositions thereof are presented in thetable) were accurately weighed in amounts presented in the followingTable 2 and defoamed and mixed at 100° C. using a vacuum stirrer toproduce a uniform dispersing medium, and the viscosity in the rotationalviscometer was obtained. In addition, a catalyst was uniformly added soas to be wt % presented in the following Table 2 in terms of outerweight % with respect to the dispersing medium and DSC measurement wasperformed, and a curing calorific value and a curing exothermic peaktemperature were obtained. Then, the powder composition (ReferenceExample 1) presented in Table 2 was defoamed and mixed with thedispersing medium before adding a catalyst at 100° C. using theabove-described vacuum stirrer until the concentration of the highthermal conductive filler particles was 40 wt % and using a kneader fromthe concentration of the high thermal conductive filler particles of 50wt % to produce a uniform dispersion liquid. The respective dispersionliquids were used as Examples 1 to 9.

The viscosity of each dispersion liquid produced above was measuredusing a rotational viscometer and/or a capillary viscometer to obtainthe viscosity. The viscosity in the rotational viscometer exhibited athixotropic property, and a viscosity value at a shear velocity of 3.4s⁻¹ at which the viscosity value is stabilized was employed. Theviscosity in the capillary viscometer was measured at a load of 300 kg,and the flow value was at around 5 ml/s (at around 50,000 s⁻¹ in termsof shear velocity). Further, the dispersing medium added with thecatalyst was subjected to the segregation stability test and the DSCmeasurement at 100° C. for 8 hours to obtain a separation degree, and amelting point of the thermoplastic polymer, curing exothermic peaktemperature, and curing calorific value. The obtained results arepresented in the following Table 2.

Press molding was performed in such a manner that each dispersion liquidcomposition of Table 2 which contains a catalyst was inserted into amold having a size of 100 mm in length×100 mm in width to have athickness of 10 mm, put in a thermostatic chamber set at 150° C.,subjected to preliminary curing for about 20 minutes, then subjected tocuring reaction at a mold setting temperature of 170° C. for 4 hoursunder a pressure of 0 to 3 MPa using a vacuum heat press machine toincrease a degree of cure, then heated to a mold setting temperature of300° C. at a rate of 5° C./min under a pressure of 0 to 10 MPa (0 to 102kgf/cm²), and cooled and solidified after being maintained for 30minutes. From the obtained molded article, the thermal conductivity bythe hot disc method and the temperature gradient method, the electricalconductivity by a high resistance measurement apparatus, a 10% weightloss temperature by TG, the bending strength, the flexural modulus ofelasticity, and the Charpy impact value were obtained. The resultsthereof are presented in the following Table 2.

TABLE 2 Example and Comparative Example Example 1 Example 2 Example 3Example 4 Example 5 Dispersion liquid composition Concentration (wt %)of high thermal conductive filler particles 30   40   50   60   40  Type of powder composition Reference Reference Reference ReferenceReference Example 1 Example 1 Example 1 Example 1 Example 1 Used amount(parts by weight) of powder composition 100    100    100    100   100    Composition and used amount of dispersing medium F-a typebenzoxazine (wt %) 5   5   5   5   5   Phenol-based epoxy resin (wt %)55   55   55   55   73   Epoxy-based reactive diluent (wt %) 40   40  40   40   22   Epoxy-modified silicone resin (wt %) 0   0   0   0   0  Amine-modified silicone resin (wt %) 0   0   0   0   0   Used amount(parts by weight) of dispersing medium 167    100    60   33   100   Physical properties of dispersing medium Viscosity (mPa · s) inrotational viscometer 7   7   7   7   7   Catalyst (outer weight % withrespect to dispersing medium) 5.0 5.0 5.0 5.0 5.0 Used amount (parts byweight) of catalyst 8.3 5.0 3.0 1.7 5.0 Curing calorific value (J/g) inDSC 268    268    268    268    270    Curing exothermic peaktemperature (° C.)^(※) in DSC 157; 266 157; 266 157; 266 157; 266 157;249 Means for producing dispersion liquid Vacuum Vacuum Kneader KneaderVacuum stirrer stirrer stirrer Physical properties of dispersion liquidcomposition Viscosity (mPa · s) in rotational viscometer 560   17,500    — — 17,000    Viscosity (Pa · s) in capillary viscometer140    145    150    155    147    Separation stability test at 100° C.(separation degree %) 0   0   0   0   0   Melting point (° C.)^(※) ofthermoplastic polymer 294    294    294    294    294    Degree of cure(%) at 170° C. 77   74   65   55   75   Degree of cure (%) at 270° C.99   99   99   99   99   Physical properties of dispersion liquidcomposition molded article Thermal conductivity (W/mK) by hot discmethod 2.9 4.0 14   18   3.9 Thermal conductivity (W/mK) by temperaturegradient method 1.8 2.2 6.9 8.8 2.3 Anisotropy in thermal conductivity1.6 1.8 2.0 2.1 1.7 Electrical conductivity ((Ωcm)⁻¹) <10⁻¹⁴  <10⁻¹⁴ <10⁻¹⁴  <10⁻¹⁴  <10⁻¹⁴  10% weight loss temperature (° C.) 399    403   412    413    402    Bending strength (MPa) 40   38   35   34   42  Flexural modulus of elasticity (GPa) 3.9 5.4 7.7 8.6 5.8 Charpy impactstrength (kJ/m²) 1.3 1.2 1.1 1.0 1.1 Example and Comparative ExampleExample 6 Example 7 Example 8 Example 9 Dispersion liquid compositionConcentration (wt %) of high thermal conductive filler particles 40  40   40   40   Type of powder composition Reference Reference ReferenceReference Example 1 Example 1 Example 1 Example 1 Used amount (parts byweight) of powder composition 100    100    100    100    Compositionand used amount of dispersing medium F-a type benzoxazine (wt %) 11  22   5   5   Phenol-based epoxy resin (wt %) 67   56   55   55  Epoxy-based reactive diluent (wt %) 22   22   20   20   Epoxy-modifiedsilicone resin (wt %) 0   0   20   0   Amine-modified silicone resin (wt%) 0   0   0   20   Used amount (parts by weight) of dispersing medium100    100    100    100    Physical properties of dispersing mediumViscosity (mPa · s) in rotational viscometer 11   30   7   10   Catalyst(outer weight % with respect to dispersing medium) 5.0 5.0 5.0 1.0 Usedamount (parts by weight) of catalyst 5.0 5.0 5.0 1.0 Curing calorificvalue (J/g) in DSC 266    255    260    263    Curing exothermic peaktemperature (° C.)^(※) in DSC 158; 263 159; 274 157; 265 154; 266 Meansfor producing dispersion liquid Vacuum Vacuum Vacuum Vacuum stirrerstirrer stirrer stirrer Physical properties of dispersion liquidcomposition Viscosity (mPa · s) in rotational viscometer 21,500   26,500    15,200    20,400    Viscosity (Pa · s) in capillary viscometer150    158    140    147    Separation stability test at 100° C.(separation degree %) 0   0   0   0   Melting point (° C.)^(※) ofthermoplastic polymer 294    294    294    294    Degree of cure (%) at170° C. 74   73   70   82   Degree of cure (%) at 270° C. 99   99   99  99   Physical properties of dispersion liquid composition molded articleThermal conductivity (W/mK) by hot disc method 3.8 4.2 4.4 4.0 Thermalconductivity (W/mK) by temperature gradient method 2.1 2.5 2.3 2.1Anisotropy in thermal conductivity 1.8 1.7 1.9 1.9 Electricalconductivity ((Ωcm)⁻¹) <10⁻¹⁴  <10⁻¹⁴  <10⁻¹⁴  <10⁻¹⁴  10% weight losstemperature (° C.) 401    402    405    401    Bending strength (MPa)48   56   35   37   Flexural modulus of elasticity (GPa) 6.0 7.3 4.0 5.2Charpy impact strength (kJ/m²) 1.3 1.4 2.1 1.2 ^(※)The former is a firstpeak temperature and the latter is a second peak temperature.

As understood from the results of Examples presented in Table 2, thethermal conductivity was increased with an increase in concentration ofthe high thermal conductive filler. Further, from the slope of thetangent, it was found that the percolation threshold of the thermalconductivity is between 20 wt % and 30 wt % of the filler concentrationand it was found that by covering the vicinity of the filler with fineorganic polymer particles, the percolation threshold is shifted to a lowconcentration side.

FIG. 1 illustrates photographs showing results of SEM observation and Natom mapping of molded articles produced in Example 2 (fillerconcentration 40 wt %) and Example 4 (filler concentration 60 wt %).Regarding the systems of these examples, filler particles having agraphite-like structure are formed from hexagonal boron nitride(containing N atom), organic polymer particles are formed from a PPSresin (containing C and S atoms), and a reactive dispersing medium isformed from a benzoxazine resin (containing C, N, and O atoms), aphenol-based epoxy resin (containing C and O atoms), and an epoxyreactive diluent (containing C and O atoms).

Herein, black island parts of FIG. 1 can be confirmed to be a PPS resinfrom the S atom mapping and form filler-non-rich phases. White parts ofFIG. 1 are hexagonal boron nitride and a benzoxazine resin which containN atoms (the content is predominantly large in the former), but becomesea parts (continuous phases) which are micro-dispersed and formfiller-rich phases. From C and O atom mappings, it is found that thehexagonal boron nitride and the reactive dispersing medium are entangledand micro-dispersed, and from comparison between the upper diagram andthe lower diagram, it is found that by increasing the fillerconcentration, the N atom concentration, that is, the concentration ofhexagonal boron nitride is significantly increased. The PPS resin whichhas poor compatibility with hexagonal boron nitride (a large differencein surface free energy) forms an island part as a filler-non-rich phaseand there are observed a lot of island parts having a length (diameter)of 50μ or more. This island part becomes larger than the particle sizeof the PPS resin in the powder composition and is considered to bemelted and aggregated/solidified.

Comparative Examples 1 to 5

The experiment was conducted according to Example 1 mentioned above,except that the concentration of the high thermal conductive fillerparticles, the type of powder composition (Reference Example 1 orComparative Reference Example 1) and the used amount thereof, and theused amounts of the dispersing medium and the catalyst were changed asthe following Table 3. The results thereof are presented as ComparativeExamples 1 to 5 in the following Table 3.

TABLE 3 Example and Comparative Example Comparative ComparativeComparative Comparative Comparative Example 1 Example 2 Example 3Example 4 Example 5 Dispersion liquid composition Concentration (wt %)of high thermal conductive 20   70 50   40   50   filler particles Typeof powder composition Reference Reference Reference ComparativeComparative Example 1 Example 1 Example 1 Reference Reference Example 1Example 1 Used amount (parts by weight) of powder composition 100    100100    100    100    Composition and used amount of dispersing mediumF-a type benzoxazine (wt %) 5   5 5   5   5   Phenol-based epoxy resin(wt %) 55   55 55   55   55   Epoxy-based reactive diluent (wt %) 40  40 40   40   40   Epoxy-modified silicone resin (wt %) 0   0 0   0   0  Amine-modified silicone resin (wt %) 0   0 0   0   0   Used amount(parts by weight) of dispersing medium 300    14.3 100    150    100   Physical properties of dispersing medium Viscosity (mPa · s) inrotational viscometer 7   7 7   7   7   Catalyst (outer weight % withrespect to dispersing medium) 5.0 5.0 1.0 5.0 5.0 Used amount (parts byweight) of catalyst 15.0  0.7 1.0 7.5 5.0 Curing calorific value (J/g)in DSC 268    268 24   268    268    Curing exothermic peak temperature(° C.)^(※) in DSC 157; 266 157; 266 174; 265 157; 266 157; 266 Means forproducing dispersion liquid Vacuum stirrer Kneader Kneader Vacuumstirrer Kneader Physical properties of dispersion liquid composition(Uniform mixing cannot be performed) Viscosity (mPa · s) in rotationalviscometer 145    — — 10,400    — Viscosity (Pa · s) in capillaryviscometer — — 150    147    153    Separation stability test at 100° C.(separation degree %) 0   — 0   15   10   Melting point (° C.) ofthermoplastic polymer 294    294 294    — — Degree of cure (%) at 170°C. 75   — 10   75   67   Degree of cure (%) at 270° C. 99   — 65   99  99   Physical properties of dispersion liquid composition molded —article Thermal conductivity (W/mK) by hot disc method 1.0 — 1.8 2.2 5.2Thermal conductivity (W/mK) by temperature gradient 0.7 — 1.2 1.1 2.3method Anisotropy in thermal conductivity 1.4 — 1.5 2.0 2.3 Electricalconductivity ((Ωcm)⁻¹) <10⁻¹⁴  — <10⁻¹⁴  <10⁻¹⁴  <10⁻¹⁴  10% weight losstemperature (° C.) 385    — 350    400    410    Bending strength (MPa)47   — 28   33   32   Flexural modulus of elasticity (GPa) 3.7 — 2.5 3.63.5 Charpy impact strength (kJ/m²) 1.0 — 1.8 0.8 0.7 ^(※)The former is afirst peak temperature and the latter is a second peak temperature.

As understood from the results of Examples 1 to 4 and ComparativeExamples 1 and 2, the thermal conductivity was increased with anincrease in concentration of the high thermal conductive filler.Further, from the slope of the tangent, it was found that thepercolation threshold of the thermal conductivity exists between fillerconcentrations of 20 wt % to 30 wt %, and it is found that, when thefiller concentration becomes 70 wt %, the powder composition and thedispersing medium are difficult to uniformly mix (Comparative Example 2)and fluidity of the dispersion liquid cannot be provided. Further, basedon comparison between Examples 2 and 3 and Comparative Examples 3 and 4,it is found that the present invention is excellent in segregationstability, thermal conductivity, bending strength, flexural modulus ofelasticity, and Charpy impact strength.

Examples 10 to 17 and Comparative Examples 6 and 7: Influence of PowderComposition on Dispersion Liquid Composition

The experiment was conducted according to Example 1 mentioned above,except that the concentration of the high thermal conductive fillerparticles, the type of powder composition (Reference Examples 2 to 8 andComparative Reference Example 2) and the used amount thereof, and theused amounts of the dispersing medium and the catalyst were changed asthe following Table 4 and the mold setting temperature in Examples 13and 17 was changed to 240° C. The results thereof are presented asExamples 10 to 17 and Comparative Examples 6 and 7 in the followingTable 4.

TABLE 4 Example and Comparative Example Example 10 Example 11 Example 12Example 13 Example 14 Dispersion liquid composition Concentration (wt %)of high thermal conductive filler particles 40   40   40   50 40 Type ofpowder composition Reference Reference Reference Reference ReferenceExample 2 Example 3 Example 4 Example 8 Example 5 Used amount (parts byweight) of powder composition 100    100    100    100  100 Used amount(parts by weight) of dispersing medium 100    100    100    60 100Catalyst (outer weight % with respect to dispersing medium) 5   5   5   5 5 Imidazole A (parts by weight) 5.0 5.0 5.0   3.0 5.0 Physicalproperties of dispersion liquid composition Viscosity (mPa · s) inrotational viscometer 17,600    17,700    18,500    — 19,800 Viscosity(Pa · s) in capillary viscometer 147    148    150    157  155Separation stability test at 100° C. (separation degree %) 0   0   0   0 0 Melting point (° C.)^(※) of thermoplastic polymer 294    75,294   294    223  294 Degree of cure (%) at 170° C. 72   78   78   75 70Degree of cure (%) at 270° C. 99   99   99   99 99 Physical propertiesof dispersion liquid composition molded article Thermal conductivity(W/mK) by hot disc method 3.7 3.9 3.7 13 6.5 Thermal conductivity (W/mK)by temperature gradient method 2.3 2.4 2.2   6.6 3.8 Anisotropy inthermal conductivity 1.6 1.6 1.7   2.0 1.7 Electrical conductivity((Ωcm)⁻¹) <10⁻¹⁴  <10⁻¹⁴  <10⁻¹⁴   <10−¹⁴ — Electrical conductivity(surface) ((Ωcm)⁻¹) — — — — 0.00033 Electrical conductivity(cross-section) ((Ωcm)⁻¹) — — — — 0.00014 Anisotropy in electricalconductivity — — — — 2.4 10% weight loss temperature (° C.) 400   420    402    409  405 Bending strength (MPa) 36   42   35   34 39Flexural modulus of elasticity (GPa) 5.5 6.5 5.4   7.3 5.6 Charpy impactstrength (kJ/m²) 1.0 1.5 0.9   1.0 1.4 Example and Comparative ExampleComparative Comparative Example 15 Example 16 Example 17 Example 6Example 7 Dispersion liquid composition Concentration (wt %) of highthermal conductive filler particles 50 40 40 40 50 Type of powdercomposition Reference Reference Reference Comparative ComparativeExample 5 Example 6 Example 7 Reference Reference Example 2 Example 2Used amount (parts by weight) of powder composition 100 100 100 100 100Used amount (parts by weight) of dispersing medium 60 100 100 150 100Catalyst (outer weight % with respect to dispersing medium) 5 5 5 5 5Imidazole A (parts by weight) 3.0 5.0 5.0 7.5 5.0 Physical properties ofdispersion liquid composition Viscosity (mPa · s) in rotationalviscometer — 19,900 19,500 10,600 — Viscosity (Pa · s) in capillaryviscometer 158 156 154 146 149 Separation stability test at 100° C.(separation degree %) 0 0 0 14 8 Melting point (° C.)^(※) ofthermoplastic polymer 294 294 223 — — Degree of cure (%) at 170° C. 6363 65 72 65 Degree of cure (%) at 270° C. 99 99 99 99 99 Physicalproperties of dispersion liquid composition molded article Thermalconductivity (W/mK) by hot disc method 11 6.3 6.2 4.3 7.5 Thermalconductivity (W/mK) by temperature gradient method 5.3 3.7 3.6 1.7 2.9Anisotropy in thermal conductivity 2.1 1.7 1.7 2.5 2.6 Electricalconductivity ((Ωcm)⁻¹) — — — — — Electrical conductivity (surface)((Ωcm)⁻¹) 0.00086 0.00031 0.00030 0.00015 0.00033 Electricalconductivity (cross-section) ((Ωcm)⁻¹) 0.00029 0.00013 0.00011 0.000050.00009 Anisotropy in electrical conductivity 3.0 2.4 2.7 3.0 3.7 10%weight loss temperature (° C.) 410 403 395 405 415 Bending strength(MPa) 37 39 37 35 34 Flexural modulus of elasticity (GPa) 7.8 5.6 5.43.8 3.5 Charpy impact strength (kJ/m²) 1.3 0.9 0.8 1.0 0.8 ^(※)Theformer is a first peak temperature and the latter is a second peaktemperature.

Regarding Examples 10 to 12, the same results as in Example 2 wereobtained. Further, regarding Examples 14 to 17, by using graphite as thehigh thermal conductive filler particles, a molded article exhibitedelectrical conductivity and had higher thermal conductivity. Based oncomparison between Examples 14 and 15 and Comparative Examples 6 and 7,it is found that the present invention is excellent in segregationstability, thermal conductivity, electrical conductivity, and mechanicalcharacteristics.

Examples 18 to 25 and Comparative Examples 8 and 9: Preparation Examplesof Dispersion Liquid Compositions Using Thermoplastic Polymer asDispersing Medium

Powder compositions in the types and used amounts presented in thefollowing Table 5 were respectively pulverized and mixed at roomtemperature with a ball mill for 4 hours to obtain powder compositions.Next, the powder compositions and dispersing media in the types and usedamounts presented in the following Table 5 were added to the ball milland then pulverized and mixed for 2 hours to obtain dispersion liquidcompositions, and the dispersion liquid compositions were regarded asExamples 18 to 22. Further, regarding Comparative Examples 8 and 9,powder compositions and dispersing media were put into a ball mill andthen pulverized and mixed for 6 hours to obtain dispersion liquidcompositions.

Each dispersion liquid composition produced above was loaded in a moldhaving a size of 40 mm in length×40 mm in width, and heated to a moldsetting temperature of 300° C. using a vacuum pressing machine and heldfor 60 minutes to perform press molding. The physical properties of thedispersion liquid composition and the physical properties of thedispersion liquid molded article were measured according to Example 1,and the results thereof are presented as Examples 18 to 22 andComparative Examples 8 and 9 in the following Table 5.

Further, 100 parts by weight of the powder composition obtained inReference Example 7 and the PP resin in an amount presented in Table 5were kneaded at a temperature equal to or higher than the melting point(147° C.) of the PP resin and equal to or lower than the melting point(223° C.) of nylon 6 using a twin-screw extruder KZW20-30WG manufacturedby TECHNOVEL CORPORATION to produce a pellet (dispersion liquidcomposition), and the pellet was subjected to injection molding at atemperature near the melting point of nylon 6 using an injection moldingmachine M-20A-SJC manufactured by Meiki Co., Ltd. (mold clamping force:20 t; screw diameter: 20 MPa) to obtain a molded article. Two moldedarticles thus obtained were superimposed, loaded in a mold having a sizeof 40 mm in length×40 mm in width, heated to a mold setting temperatureof 300° C. using a vacuum pressing machine, and held for 60 minutes toperform press molding, thereby obtaining a specimen. The physicalproperties of the dispersion liquid composition and the physicalproperties of the dispersion liquid molded article are measuredaccording to Example 1, and the results thereof are presented asExamples 23 to 25 in Table 5.

TABLE 5 Example and Comparative Example Example 18 Example 19 Example 20Example 21 Example 22 Example 23 Dispersion liquid compositionConcentration (wt %) of high thermal conductive filler 40 50 60 64 6030   particles Type of powder composition Reference Reference ReferenceReference Reference Reference Example 7 Example 7 Example 7 Example 7Example 6 Example 7 Used amount (parts by weight) of powder composition100 100 100 100 100 100    Type and used amount of dispersing mediumNylon 6 resin (parts be weight) 0 0 0 0 33 0   PP resin (parts byweight) 100 60 33 25 0 167    Physical properties of dispersion liquidcomposition Viscosity (mPa · s) in capillary viscometer 147 161 168 172185 141    Melting point (° C.)^(※) of thermoplastic polymer 147,223147,223 147,223 147,223 223,294 147,223     Separation stability test(separation degree %) 0 0 0 0 0 0   Physical properties of dispersionliquid composition molded article Thermal conductivity (W/mK) by hotdisc method 6.6 11 20 26 24 3.2 Thermal conductivity (W/mK) bytemperature gradient 4.4 6.3 12 15 14 1.1 method Anisotropy in thermalconductivity 1.5 1.7 1.7 1.7 1.7 2.9 Electrical conductivity (surface)((Ωcm)⁻¹) 0.48 1.89 21 46 25 <10⁻¹⁴  Electrical conductivity(cross-section) ((Ωcm)⁻¹) 0.28 0.71 7.1 14 7.5 <10⁻¹⁴  Anisotropy inelectrical conductivity 1.7 2.7 3.0 3.3 3.3 — 10% weight losstemperature (° C.) 429 432 433 434 445 430    Bending strength (MPa) 5.915 16 18 18 3.9 Flexural modulus of elasticity (GPa) 1.7 2.7 4.3 5.5 5.41.6 Example and Comparative Example Comparative Comparative Example 24Example 25 Example 8 Example 9 Dispersion liquid compositionConcentration (wt %) of high thermal conductive filler 40 50 40 50particles Type of powder composition Reference Reference ComparativeComparative Example 7 Example 7 Reference Reference Example 2 Example 2Used amount (parts by weight) of powder composition 100 100 100 100 Typeand used amount of dispersing medium Nylon 6 resin (parts be weight) 0 00 0 PP resin (parts by weight) 100 60 150 100 Physical properties ofdispersion liquid composition Viscosity (mPa · s) in capillaryviscometer 147 161 150 157 Melting point (° C.)^(※) of thermoplasticpolymer 147,223 147,223 147 147 Separation stability test (separationdegree %) 0 0 12 7 Physical properties of dispersion liquid compositionmolded article Thermal conductivity (W/mK) by hot disc method 4.6 11 4.57.8 Thermal conductivity (W/mK) by temperature gradient 1.5 5.0 1.8 3.1method Anisotropy in thermal conductivity 3.1 2.2 2.5 2.5 Electricalconductivity (surface) ((Ωcm)⁻¹) 1.2 × 10⁻⁸ 8.5 × 10⁻³ 0.20 1.10Electrical conductivity (cross-section) ((Ωcm)⁻¹) 2.4 × 10⁻⁹ 2.1 × 10⁻³0.06 0.30 Anisotropy in electrical conductivity 5.0 4.0 3.3 3.7 10%weight loss temperature (° C.) 432 434 415 422 Bending strength (MPa)4.3 10 5.1 5.6 Flexural modulus of elasticity (GPa) 2.6 5.0 1.7 2.1^(※)The former is a first peak temperature and the latter is a secondpeak temperature.

From Examples 18 to 21, it is found that the thermal conductivity, theelectrical conductivity, and the mechanical strength are increased asthe concentration of the high thermal conductive filler particlesincreases, and a thermal conductive infinite cluster is formed. Inaddition, from comparison between Example 20 and Example 22, it is foundthat by changing the dispersing medium from the PP resin to the nylon 6resin, the thermal conductivity, the electrical conductivity, and themechanical strength are improved. Further, from comparison betweenExamples 18 and 19 and Comparative Examples 8 and 9, it is found thatthe present invention is excellent in thermal conductivity, theelectrical conductivity, and the mechanical characteristics.Furthermore, from Examples 23 to 25, it was found that by injectionmolding the dispersion liquid composition, almost the same effect as inheat press molding is obtained and productivity can be significantlyimproved.

Example 26 and Comparative Example 10: Two-Color Molding UsingInsulating/Conductive Material

A conductive material dispersion liquid composition (thermalconductivity 24 W/mK, surface electrical conductivity 25 (Ωcm)⁻¹) wasproduced in the similar manner to Example 22, was loaded into a moldhaving a size of 100 mm in length×100 mm in width to have a depth of 5mm, and molded according to Example 22. Thereafter, the insulatingmaterial dispersion liquid composition obtained in Example 13 (thermalconductivity 13 W/mK, electrical conductivity 10⁻¹⁴ (Ωcm)⁻¹ or less) wasloaded into the upper part of the conductive material molded article tohave a depth of 5 mm, cured/molded according to Example 13, and thensubjected to insulation/conductive material two-color molding. Thephysical properties of the obtained dispersion liquid composition moldedarticle are presented in the following Table 5 as Example 26. Inaddition, the experiment was performed in the similar manner to Example26 using Comparative Example 7 (thermal conductivity 7.5 W/mK,electrical conductivity 1.0 (Ωcm)⁻¹) as the insulating materialdispersion liquid composition instead of Example 13. The results thereofare presented in the following Table 6 as Comparative Example 10.Incidentally, the measurement of the thermal conductivity by the hotdisc method was performed from both sides of the insulating material andthe conductive material, and the measurement of the thermal conductivityby the temperature gradient method was performed by heating from theinsulating material side. The measurement of the electrical conductivityon the surface was also performed from both sides of the insulatingmaterial and the conductive material, and the measurement of theelectrical conductivity on the cross-section was performed by energizingfrom both sides of the insulating material and the conductive material.

TABLE 6 Example and Comparative Example Comparative Example 26 Example10 Electrical characteristics of material Conductive InsulatingConductive Insulating material material material material Dispersionliquid composition Example 22 Example 13 Example 22 Comparative Example7 Concentration (wt %) of hiqh thermal conductive filler particles 60 5060 50 Physical properties of dispersion liquid composition moldedarticle Thermal conductivity (W/mK) by hot disc method From insulatingside 12 5.0 From conductive side 23 22   Thermal conductivity (W/mK) bytemperature gradient method 10 1.8 Electrical conductivity (surface)((Ωcm)⁻¹) From insulating side  <10⁻¹⁴ <10⁻¹⁴  From conductive side  7.6 0.5 Electrical conductivity (cross-section) ((Ωcm)⁻¹)  <10⁻¹⁴<10⁻¹⁴  Bending strength (MPa) 32 18   Flexural modulus of elasticity(GPa)   7.0 3.5

From comparison between Example 26 and Comparative Example 10, it isfound that the present invention is excellent in electrical conductiveand mechanical characteristics. Incidentally, in Comparative Example 10,since sufficient bonding cannot be performed at the interface betweenthe insulating material and the conductive material, peeling-off at theinterface occurred in the bending test.

FIG. 2 illustrates a photograph showing a result of SEM observation of amolded article produced in Example 26. The dashed line at the centerindicates the interface between the insulating material (Example 13) andthe conductive material (Example 22), the left half corresponds to theinsulating material, and the right half corresponds to the conductivematerial. From the SEM photograph, it was found that there aredistinctive agglomerations of A, B, and C.

FIG. 3 illustrates photographs showing results of S, C, N, and O atommapping obtained by EDX analysis in the SEM photograph shown in FIG. 2.The insulating material is formed from hexagonal boron nitride(containing N atom) as the filler having a graphite-like structure and anylon 6 resin (containing C, O, and N atoms) as the organic polymerparticles, and the reactive dispersing medium is formed from abenzoxazine resin (containing C, N, and O atoms), a phenol-based epoxyresin (containing C and O atoms), and an epoxy reactive diluent(containing C and O atoms). The conductive material is formed from ascale-like graphite (containing C atom) and graphite scrap (containing Catom) as the filler having a graphite-like structure, a PPS resin(containing C and S atoms) as the organic polymer particles, and nylon 6(containing C, N, and O atoms) as the thermoplastic resin for thedispersing medium.

In the S atom mapping, a significant island part corresponding to theagglomeration B is observed and is considered to be derived from the PPSresin. In the C atom mapping, signals corresponding to theagglomerations A and C are observed and the agglomeration A of theinsulating material is considered to be an island part derived from thenylon 6 resin. The agglomeration C of the conductive material shows asignal stronger than that of the agglomeration A, it seems that graphiteis mixed with the nylon 6 resin, and the C atom mapping spreadsthroughout to form a continuous phase. In the N atom mapping, as for theinsulating material, a signal derived from hexagonal boron nitridestrongly appears, and it is considered that the hexagonal boron nitrideand the reactive dispersing medium are entangled to form a continuousphase. As for the conductive material, in a part except the island part(the agglomeration B) of the PPS resin, the N atom mapping spreads as aweak signal, and it is considered that the nylon 6 resin and thegraphite are entangled to form a continuous phase. In the O atommapping, although a signal is weak, the signal appears at parts derivedfrom the nylon 6 resin and the reactive dispersing medium.

As mentioned above, in the SEM/EDX analysis of the molded articleproduced in Example 26, it is considered that the nylon 6 resin partforms a filler-non-rich phase in the insulating material, the PPS resinpart forms a filler-non-rich phase in the conductive material, in theformer, the hexagonal boron nitride and the reactive dispersing mediumare micro-dispersed, in the latter, the nylon 6 resin and the graphiteare entangled and mixed to form a continuous phase as a filler-richphase, and both are in contact with each other at the interface andexhibit a high thermal conductivity. The formation process of thefiller-non-rich phase can be described by the difference in surface freeenergy between the filler and the resin as mentioned above.

Examples 27 and 28 and Comparative Example 11: Effect by Existence ofResin Molding of Stator

Using an outer rotor type CQ brushless motor & inverter kit for anelectric vehicle (original seller: CQ Publishing Co., Ltd.), a torquesensor and a powder brake were attached onto the rotation shaft of themotor, heat generation status in a stator coil portion and the motorperformance at the time of operating the motor were investigated, andthe effect by existence of resin molding to the stator was investigated.

FIG. 4 illustrates photographs of stators without resin molding (left)and with resin molding (right) used in motor evaluation. A resin moldhaving a three-layer structure of an exterior conductive material(filler concentration 64 wt %) obtained from the dispersion liquidcomposition of Example 22 disposed at the outside of a resin moldedstator, an interior conductive material (filler concentration 60 wt %)obtained from the dispersion liquid composition of Example 4 disposed atthe inner interface thereof, and an interior conductive material (fillerconcentration 40 wt %) obtained from the dispersion liquid compositionof Example 2 disposed inside a coil portion was disposed (Example 27).Further, an example in which a resin mold having a two-layer structurewas disposed similarly except that the conductive material (fillerconcentration 40 wt %) of Example 17 was used as an interior conductivematerial was regarded as Example 28.

A temperature sensor was attached to the inner portion of the coilportion, the motor performance and the exothermic behavior wereinvestigated, and then an increase in temperature in each number ofrevolutions at a certain torque (1.1 Nm) and an increase in temperatureat each torque in a certain number of revolutions (100 rpm) arepresented in the following Table 7. Incidentally, as presented in Table7, the case of using a stator without resin molding was regarded asComparative Example 11 and then the result of the Comparative Example 11was compared with the results of Examples 27 and 28. As a result, it wasfound that by employing resin molding in Examples, an increase intemperature at 5 to 28° C. can be prevented.

TABLE 7 Example and Comparative Example Comparative Example 27 Example28 Example 11 Exterior material Example 22 Example 22 None (conductivematerial) (conductive material) Interior material Examples 2 and 4Example 17 None (insulating material) (conductive material) Torque (Nm)1.1 1.1 0.9 1.5 1.1 1.1 0.9 1.5 1.1 1.1 0.9 1.5 Number of 100 300 100100 100 300 100 100 100 300 100 100 revolutions (rpm) Temperatureincrease 45 41 30 90 42 38 28 82 55 52 35 110 (° C.)

The present application is based on Japanese Patent Application No.2017-219202 filed on Nov. 14, 2017, the entire disclosure of which isincorporated by reference.

1-28. (canceled)
 29. A filler-loaded high thermal conductive dispersionliquid composition being formed by uniformly dispersing a powdercomposition, which contains organic polymer particles containingthermoplastic polymer particles, and high thermal conductive fillerparticles which contain filler particles having a graphite-likestructure and is obtained by pulverizing 5 to 70 parts by weight of theorganic polymer particles and 30 to 95 parts by weight of the highthermal conductive filler particles with respect to 100 parts by weightof the total amount of these components by using a pulverizing machine,which performs grinding with frictional force or impact force, to causedelamination or cohesive failure while maintaining an average planarparticle size of the filler particles having a graphite-like structure,in the powder composition, the vicinity of the high thermal conductivefiller particles being covered with the micronized organic polymerparticles and the covered particles being uniformly dispersed, using 25to 250 parts by weight of a liquid reactive dispersing medium and/or adispersing medium containing a thermoplastic polymer having a deflectiontemperature under load or a melting point lower than that of thethermoplastic polymer used in the powder composition by 5 to 150° C.with respect to 100 parts by weight of the powder composition, and thedispersion liquid composition having conditions that a thermalconductive infinite cluster exhibiting a thermal conductivity of 1 to 35W/mK is formed and a concentration of the high thermal conductive fillerparticles is equal to or more than a percolation threshold.
 30. Thefiller-loaded high thermal conductive dispersion liquid compositionaccording to claim 29, wherein the dispersing medium comprises theliquid reactive dispersing medium.
 31. The filler-loaded high thermalconductive dispersion liquid composition according to claim 29, whereinthe dispersing medium does not comprise the liquid reactive dispersingmedium.
 32. The filler-loaded high thermal conductive dispersion liquidcomposition according to claim 29, wherein the dispersing medium doesnot comprise the thermoplastic polymer having a deflection temperatureunder load or a melting point lower than that of the thermoplasticpolymer used in the powder composition by 5 to 150° C.
 33. Thefiller-loaded high thermal conductive dispersion liquid compositionaccording to claim 29, wherein the pulverizing machine is a ball mill, aroller mill, a bead mill, or a medium mill.
 34. The filler-loaded highthermal conductive dispersion liquid composition according to claim 29,wherein the thermoplastic polymer particles used in the powdercomposition contain at least one selected from the group consisting of athermoplastic resin and a thermoplastic elastomer, all of which havecrystallinity and/or aromaticity.
 35. The filler-loaded high thermalconductive dispersion liquid composition according to claim 29, whereinthe thermoplastic polymer particles used in the powder compositioncontain at least one selected from the group consisting of polyphenylenesulfide, polyethylene terephthalate, polybutylene terephthalate,polycarbonate, polyamide, polyethylene, and polypropylene.
 36. Thefiller-loaded high thermal conductive dispersion liquid compositionaccording to claim 29, wherein the filler particles having agraphite-like structure are hexagonal boron nitride particles and athermal conductivity thereof is 1 to 25 W/mK.
 37. The filler-loaded highthermal conductive dispersion liquid composition according to claim 36,wherein the high thermal conductive filler particles further containmagnesium oxide particles.
 38. The filler-loaded high thermal conductivedispersion liquid composition according to claim 29, wherein the highthermal conductive filler particles contain graphite particles and athermal conductivity thereof is 3 to 35 W/mK.
 39. The filler-loaded highthermal conductive dispersion liquid composition according to claim 38,wherein the graphite particles contain natural graphite particles and/orartificial graphite particles.
 40. The filler-loaded high thermalconductive dispersion liquid composition according to claim 39, whereinthe natural graphite particles contain scale-like graphite particles.41. The filler-loaded high thermal conductive dispersion liquidcomposition according to claim 29, wherein the liquid dispersing mediumcontains the reactive dispersing medium and the reactive dispersingmedium contains an uncured thermosetting resin.
 42. The filler-loadedhigh thermal conductive dispersion liquid composition according to claim41, wherein the uncured thermosetting resin contains a benzoxazine resinand/or a phenol-based epoxy resin.
 43. The filler-loaded high thermalconductive dispersion liquid composition according to claim 41, whereinthe uncured thermosetting resin contains an epoxy reactive diluentand/or an epoxy-modified silicone resin.
 44. The filler-loaded highthermal conductive dispersion liquid composition according to claim 41,wherein the liquid reactive dispersing medium contains a curing agent.45. The filler-loaded high thermal conductive dispersion liquidcomposition according to claim 44, wherein the curing agent contains atleast one resin selected from the group consisting of an amine-modifiedsilicone resin, an alcohol-modified silicone resin, and a carboxylicacid-modified silicone resin.
 46. The filler-loaded high thermalconductive dispersion liquid composition according to claim 41, whereinthe liquid reactive dispersing medium contains a catalyst.
 47. Thefiller-loaded high thermal conductive dispersion liquid compositionaccording to claim 43, wherein the catalyst contains an imidazolecompound.
 48. The filler-loaded high thermal conductive dispersionliquid composition according to claim 29, wherein the dispersing mediumcontains the thermoplastic polymer and a deflection temperature underload or a melting point of the thermoplastic polymer is lower than thatof the thermoplastic polymer particles used in the powder composition by10 to 100° C.
 49. The filler-loaded high thermal conductive dispersionliquid composition according to claim 29, wherein a viscosity at atemperature at the time of cast molding or potting is 100 mPa·s or moreand 300 Pa·s or less.
 50. The filler-loaded high thermal conductivedispersion liquid composition according to claim 29, wherein the thermalconductive infinite cluster is based on a high thermal conductivefiller-rich phase mainly attributable to the powder composition.
 51. Amethod for producing a filler-loaded high thermal conductive dispersionliquid composition, the method comprising: a step (1) of obtaining apowder composition, which contains organic polymer particles containingthermoplastic polymer particles, and high thermal conductive fillerparticles which contain filler particles having a graphite-likestructure, by pulverizing 5 to 70 parts by weight of the organic polymerparticles and 30 to 95 parts by weight of the high thermal conductivefiller particles with respect to 100 parts by weight of the total amountof these components by using a pulverizing machine, which performsgrinding with frictional force or impact force, to cause delamination orcohesive failure while maintaining an average planar particle size ofthe filler particles having a graphite-like structure, in the powdercomposition, the vicinity of the high thermal conductive fillerparticles being covered with the micronized organic polymer particlesand the covered particles being uniformly dispersed; and a step (2) ofuniformly dispersing the powder composition using 25 to 250 parts byweight of a liquid reactive dispersing medium and/or a dispersing mediumcontaining a thermoplastic polymer having a deflection temperature underload or a melting point lower than that of the thermoplastic polymerparticles used in the powder composition by 5 to 150° C. with respect to100 parts by weight of the powder composition to prepare a dispersionliquid composition having conditions that a thermal conductive infinitecluster exhibiting a thermal conductivity of 1 to 35 W/mK is formed anda concentration of the high thermal conductive filler is equal to ormore than a percolation threshold.
 52. A filler-loaded high thermalconductive material being formed by uniformly dispersing a powdercomposition, which contains organic polymer particles containingthermoplastic polymer particles, and high thermal conductive fillerparticles which contain filler particles having a graphite-likestructure and is obtained by pulverizing 5 to 70 parts by weight of theorganic polymer particles and 30 to 95 parts by weight of the highthermal conductive filler particles with respect to 100 parts by weightof the total amount of these components by using a pulverizing machine,which performs grinding with frictional force or impact force, to causedelamination or cohesive failure while maintaining an average planarparticle size of the filler particles having a graphite-like structure,in the powder composition, the vicinity of the high thermal conductivefiller particles being covered with the micronized organic polymerparticles and the covered particles being uniformly dispersed, using 25to 400 parts by weight of a liquid reactive dispersing medium and/or adispersing medium containing a thermoplastic polymer having a deflectiontemperature under load or a melting point lower than that of thethermoplastic polymer used in the powder composition by 5 to 150° C.with respect to 100 parts by weight of the powder composition, and bycausing a dispersion liquid composition having conditions that a thermalconductive infinite cluster exhibiting a thermal conductivity of 1 to 35W/mK is formed and a concentration of the high thermal conductive filleris equal to or more than a percolation threshold to react under acondition that the liquid reactive dispersing medium forms a crosslinkedpolymer when the dispersing medium comprises the liquid reactivedispersing medium, or to be fluidized at a temperature that is equal toor lower than a deflection temperature under load or a melting point ofthe thermoplastic polymer particles used in the powder composition andis equal to or higher than a deflection temperature under load or amelting point of the thermoplastic polymer used in the dispersing mediumwhen the dispersing medium comprises the thermoplastic resin, then to bemolded by heating at a pressure of 0 to 1000 kgf/cm² and at atemperature equal to or higher than a deflection temperature under loador a melting point of the thermoplastic polymer particles used in thepowder composition, and cooled and solidified, wherein the filler-loadedhigh thermal conductive material contains a high thermal conductivefiller-rich phase and a high thermal conductive filler-non-rich phaseand the high thermal conductive filler-rich phase forms a thermalconductive infinite cluster.
 53. The filler-loaded high thermalconductive material according to claim 52, wherein the high thermalconductive filler rich phase consists of the high thermal conductivefiller and the reactive dispersing medium when the dispersing mediumcontains the liquid reactive dispersing medium.
 54. The filler-loadedhigh thermal conductive material according to claim 52, wherein the highthermal conductive filler-rich phase consists of the high thermalconductive filler and either of the thermoplastic polymer used in thepowder composition or the thermoplastic powder having a deflectiontemperature under load or a melting point lower than that of thethermoplastic polymer used in the powder composition.
 55. A method forproducing a filler-loaded high thermal conductive material, the methodcomprising: a step (1) of obtaining a powder composition, which containsorganic polymer particles containing thermoplastic polymer particles,and high thermal conductive filler particles which contain fillerparticles having a graphite-like structure, by pulverizing 5 to 70 partsby weight of the organic polymer particles and 30 to 95 parts by weightof the high thermal conductive filler particles with respect to 100parts by weight of the total amount of these components by using apulverizing machine, which performs grinding with frictional force orimpact force, to cause delamination or cohesive failure whilemaintaining an average planar particle size of the filler particleshaving a graphite-like structure, in the powder composition, thevicinity of the high thermal conductive filler particles being coveredwith the micronized organic polymer particles and the covered particlesbeing uniformly dispersed; a step (2) of uniformly dispersing the powdercomposition using 25 to 250 parts by weight of a liquid reactivedispersing medium and/or a dispersing medium containing a thermoplasticpolymer having a deflection temperature under load or a melting pointlower than that of the thermoplastic polymer particles used in thepowder composition by 5 to 150° C. with respect to 100 parts by weightof the powder composition to prepare a dispersion liquid compositionhaving conditions that a thermal conductive infinite cluster exhibitinga thermal conductivity of 1 to 35 W/mK is formed and a concentration ofthe high thermal conductive filler particles is equal to or more than apercolation threshold; a crosslinking step (3) of allowing thedispersion liquid composition to react under a condition that the liquidreactive dispersing medium forms a crosslinked polymer when thedispersing medium comprises the liquid reactive dispersing medium; afluidizing step (4) of fluidizing the thermoplastic polymer used in thedispersing medium at a temperature that is equal to or lower than adeflection temperature under load or a melting point of thethermoplastic polymer used in the powder composition and is equal to orhigher than a deflection temperature under load or a melting point ofthe thermoplastic polymer used in the dispersing medium when thedispersing medium comprises the thermoplastic resin; a step (5) ofmolding by heating the material formed in the crosslinking step (3)and/or the fluidizing step (4) at a pressure of 0 to 1000 kgf/cm² and ata temperature equal to or higher than a deflection temperature underload or a melting point of the thermoplastic polymer particles used inthe powder composition; and a step (6) of cooling and solidifying thematerial formed in the step (5).
 56. The method for producing afiller-loaded high thermal conductive material according to claim 55,wherein the condition that the liquid reactive dispersing medium forms acrosslinked polymer is that the reactive dispersing medium has a degreeof cure of 80% or more.
 57. A molded article comprising thefiller-loaded high thermal conductive material according to claim 52,the molded article being used as a high thermal conductive/heatdissipation component.
 58. A molded article comprising a filler-loadedhigh thermal conductive material produced by the production methodaccording to claim 55, the molded article being used as a high thermalconductive/heat dissipation component.
 59. The molded article accordingto claim 57, wherein the molded article is formed by laminating twolayers of the filler-loaded high thermal conductive material, one layerof the two layers has a thermal conductivity of 3 to 35 W/mK andexhibits electrical conductivity with a surface electrical conductivityof 70 (Ωcm)⁻¹ or less, and the other layer of the two layers has athermal conductivity of 1 to 25 W/mK and is a semiconductor having asurface electrical conductivity of 0.1 to 10⁻¹⁰ (Ωcm)⁻¹ or exhibitsinsulating properties with a surface electrical conductivity of 10⁻¹⁰(Ωcm)⁻¹ or less.
 60. The molded article according to claim 57, whereinlayers of the two layers of the filler-loaded high thermal conductivematerial are layers formed from gradient materials having differentfiller concentrations from each other.
 61. A method for producing amolded article being used as a high thermal conductive/heat dissipationcomponent, comprising producing the molded article by using thefiller-loaded high thermal conductive material according to claim 52.62. A method for producing a molded article being used as a high thermalconductive/heat dissipation component, comprising producing the moldedarticle by using a filler-loaded high thermal conductive materialproduced by the production method according to claim 55.